Chapter M: J. Berkeley (1)

SIBBERTOFT,

_November 23, 1874._

CONTENTS.

PAGE
I. NATURE OF FUNGI. 1
II. STRUCTURE. 17
III CLASSIFICATION 64
IV. USES. 82
V. NOTABLE PHENOMENA. 105
VI. THE SPORE AND ITS DISSEMINATION. 119
VII. GERMINATION AND GROWTH. 137
VIII. SEXUAL REPRODUCTION. 163
IX. POLYMORPHISM. 182
X. INFLUENCES AND EFFECTS. 209
XI. HABITATS. 233
XII. CULTIVATION. 253
XIII. GEOGRAPHICAL DISTRIBUTION. 266
XIV. COLLECTION AND PRESERVATION. 287
INDEX. 295

LIST OF ILLUSTRATIONS.

FIG. PAGE
1. Agaric in Process of Growth. 17
2. Section of Common Mushroom. 21
3. Sterile cells, Basidia, Cystidium, from _Gomphidius_. 21
4. _Polyporus giganteus_ (reduced). 23
5. _Hydnum repandum._ 24
6. _Calocera viscosa._ 24
7. _Tremella mesenterica._ 24
8. Basidia and spores of _Phallus_. 28
9. Basidia and spores of _Lycoperdon_. 29
10. Threads of _Trichia_. 31
11. _Arcyria incarnata_, with portion of threads and spore. 33
12. _Diachæa elegans._ 34
13. _Cyathus vernicosus._ 34
14. _Cyathus_, Sporangia and spores. 35
15. _Asterosporium Hoffmanni._ 36
16. Barren Cysts and Pseudospores of _Lecythea_. 36
17. _Coleosporium Tussilaginis._ 36
18. _Melampsora salicina_, pseudospores of 36
19. _Cystopus candidus_, conidia of 38
20. _Xenodochus carbonarius_, pseudospore. 38
21. _Phragmidium bulbosum_, pseudospores. 38
22. Pseudospores of _Puccinia_. 40
23. _Thecaphora hyalina_, pseudospores. 41
24. _Æcidium Berberidis_, peridia of 41
25. _Helminthosporium molle_, threads and spores. 42
26. _Acrothecium simplex._ 44
27. _Peronospora Arenariæ._ 44
28. _Polyactis cinerea._ 47
29. _Peziza Fuckeliana_, with ascus and sporidia. 47
30. _Penicillium chartarum._ 50
31. _Mucor mucedo_, with sporangia. 50
32. Small portion of _Botrytis Jonesii_. 54
33. Section of cup of _Ascobolus_. 57
34. Asci, sporidia, and paraphyses of _Ascobolus_. 59
35. Perithecium of _Sphæria_. 61
36. _Uncinula adunca_, conceptacle with appendages. 62
37. _Agaricus nudus._ 66
38. _Scleroderma vulgare_, Fr. 69
39. _Ceuthospora phacidioides._ 69
40. _Rhopalomyces candidus._ 74
41. _Mucor caninus._ 75
42. _Sphæria aquila_, cluster of perithecia. 78
43. _Morchella gigaspora_, from Kashmir. 99
44. _Cyttaria Gunnii_ 101
45. Spores of Agarics 121
46. Spores of _Lactarius_ 121
46a. Spores of _Gomphidius_ 122
47. Spores of _Polyporus_, _Boletus_, and _Hydnum_. 122
48. _Diachea elegans_, capellitium of 123
49. Spore of _Hendersonia polycystis_. 126
50. Spores of _Dilophospora graminis_. 126
51. Spores of _Discosia_. 126
52. Spore of _Prosthemium betulinum_. 126
53. Spore of _Stegonosporium cellulosum_. 126
54. Stylospores of _Coryneum disciforme_. 126
55. Spores of _Asterosporium Hoffmanni_. 126
56. Spores of _Pestalozzia_. 126
57. _Bispora monilioides_, concatenate spores 126
58. Pseudospores of _Thecaphora hyalina_. 128
59. Pseudospores of _Puccinia_. 128
60. Pseudospores of _Triphragmium_. 128
61. Pseudospores of _Phragmidium bulbosum_. 128
62. Winter spores of _Melampsora salicina._ 128
63. Spores of _Helicocoryne_. 129
64. Sporidium of _Genea verrucosa_. 130
65. Alveolate sporidium of _Tuber_. 130
66. Asci, sporidia, and paraphyses of _Ascobolus_. 131
67. Sporidium of _Ostreichnion Americanum_. 132
68. Ascus and sporidia of _Hypocrea_. 135
69. Sporidium of _Sphæria ulnaspora_. 135
70. Sporidia of _Valsa profusa_. 135
71. Sporidia of _Massaria foedans_. 135
72. Sporidium of _Melanconis bicornis_. 135
73. Caudate sporidia of _Sphæria fimiseda_. 135
74. Sporidia of _Valsa thelebola_. 135
75. Sporidia of _Valsa taleola_. 135
76. Sporidium of _Sporormia intermedia_. 135
77. Asci and sporidia of _Sphæria_ (_Pleospora_)
_herbarum_. 135
78. Sporidium of _Sphæria putaminum_. 135
79. Basidia and spores of _Exidia spiculosa_. 139
80. Germinating spore and corpuscles of _Dacrymyces_. 140
81. Germination of _Æcidium Euphorbia_. 142
82. Germinating pseudospores of _Coleosporium Sonchi_. 144
83. Germinating pseudospore of _Melampsora betulina_. 144
84. Germinating pseudospore of _Uromyce appendiculatus_. 145
85. Germinating pseudospore of _Puccinia Moliniæ_. 146
86. Germinating pseudospore of _Triphragmium Ulmariæ_. 146
87. Germinating pseudospore of _Phragmidium bulbosum_. 147
88. Germinating pseudospores of _Podisoma Juniperi_. 149
89. Germinating pseudospore of _Tilletia caries_. 150
90. Pseudospore of _Ustilago receptaculorum_ in germination,
and secondary spores in conjugation. 151
91. Conidia and zoospores of _Cystopus candidus_. 151
92. Resting spore of _Cystopus candidus_ with zoospores. 152
93. Zygospores of _Mucor phycomyces_. 158
94. Sporidium of _Ascobolus_ germinating. 161
95. Zygospore of _Mucor_. 164
96. Zygospore of _Rhizopus_ in different stages. 166
97. Conjugation in _Achlya racemosa_. 169
98. Conjugation in _Peronospora._ 171
99. Antheridia and oogonium of _Peronospora_. 172
100. Conjugation in _Peziza omphalodes_. 176
100a. Formation of conceptacle in _Erysiphe_. 176
101. _Tilletia caries_ with conjugating cells. 178
102. _Aspergillus glaucus_ and _Eurotium_. 190
103. _Erysiphe cichoracearum_, receptacle and mycelium. 192
104. Twig with _Tubercularia_ and _Nectria_. 193
105. Section of _Tubercularia_ with conidia. 193
106. D. _Nectria_ with _Tubercularia_, ascus and paraphyses. 195
107. Cells and pseudospores of _Æcidium berberidis_. 201
108. Cells and pseudospores of _Æcidium graveolens_. 201
109. _Torrubia militaris_ on pupa of a moth. 243

FUNGI

THEIR NATURE, USES, INFLUENCES, ETC.

I.

NATURE OF FUNGI.

The most casual observer of Nature recognizes in almost every instance that comes under his notice in every-day life, without the aid of logical definition, the broad distinctions between an animal, a plant, and a stone. To him, the old definition that an animal is possessed of life and locomotion, a plant of life without locomotion, and a mineral deficient in both, seems to be sufficient, until some day he travels beyond the circuit of diurnal routine, and encounters a sponge or a zoophyte, which possesses only one of his supposed attributes of animal life, but which he is assured is nevertheless a member of the animal kingdom. Such an encounter usually perplexes the neophyte at first, but rather than confess his generalizations to have been too gross, he will tenaciously contend that the sponge must be a plant, until the evidence produced is so strong that he is compelled to desert his position, and seek refuge in the declaration that one kingdom runs into the other so imperceptibly that no line of demarcation can be drawn between them. Between these two extremes of broad distinction, and no distinction, lies the ground occupied by the scientific student, who, whilst admitting that logical definition fails in assigning briefly and tersely the bounds of the three kingdoms, contends that such limits exist so positively, that the universal scientific mind accepts the recognized limit without controversy or contradiction.

In like manner, if one kingdom be made the subject of inquiry, the same difficulties will arise. A flowering plant, as represented by a rose or a lily, will be recognized as distinct from a fern, a seaweed, or a fungus. Yet there are some flowering plants which, at first sight, and without examination, simulate cryptogams, as, for example, many _Balanophoræ_, which the unscientific would at once class with fungi. It is nevertheless true that even the incipient botanist will accurately separate the phanerogams from the cryptogams, and by means of a little more, but still elementary knowledge, distribute the latter amongst ferns, mosses, fungi, lichens, and algæ, with comparatively few exceptions. It is true that between fungi and lichens there exists so close an affinity that difficulties arise, and doubts, and disputations, regarding certain small groups or a few species; but these are the exception, and not the rule. Botanists generally are agreed in recognizing the five principal groups of Cryptogamia, as natural and distinct. In proportion as we advance from comparison of members of the three kingdoms, through that of the primary groups in one kingdom, to a comparison of tribes, alliances, and orders, we shall require closer observation, and more and more education of the eye to see, and the mind to appreciate, relationships and distinctions.

We have already assumed that fungi are duly and universally admitted, as plants, into the vegetable kingdom. But of this fact some have even ventured to doubt. This doubt, however, has been confined to one order of fungi, except, perhaps, amongst the most illiterate, although now the animal nature of the _Myxogastres_ has scarcely a serious advocate left. In this order the early condition of the plant is pulpy and gelatinous, and consists of a substance more allied to sarcode than cellulose. De Bary insinuated affinities with _Amoeba_,[A] whilst Tulasne affirmed that the outer coat in some of these productions contained so much carbonate of lime that strong effervescence took place on the application of sulphuric acid. Dr. Henry Carter is well known as an old and experienced worker amongst amoeboid forms of animal life, and, when in Bombay, he devoted himself to the examination of the _Myxogastres_ in their early stage, and the result of his examinations has been a firm conviction that there is no relationship whatever between the _Myxogastres_ and the lower forms of animal life. De Bary has himself very much modified, if not wholly abandoned, the views once propounded by him on this subject. When mature, and the dusty spores, mixed with threads, sometimes spiral, are produced, the _Myxogastres_ are so evidently close allies of the _Lycoperdons_, or Puffballs, as to leave no doubt of their affinities. It is scarcely necessary to remark that the presence of zoospores is no proof of animal nature, for not only do they occur in the white rust (_Cystopus_), and in such moulds as _Peronospora_,[B] but are common in algæ, the vegetable nature of which has never been disputed.

There is another equally important, but more complicated subject to which we must allude in this connection. This is the probability of minute fungi being developed without the intervention of germs, from certain solutions. The observations of M. Trécul, in a paper laid before the French Academy, have thus been summarized:--1. Yeast cells may be formed in the must of beer without spores being previously sown. 2. Cells of the same form as those of yeast, but with different contents, arise spontaneously in simple solution of sugar, or to which a little tartrate of ammonia has been added, and these cells are capable of producing fermentation in certain liquids under favourable conditions. 3. The cells thus formed produce _Penicillium_ like the cells of yeast. 4. On the other hand, the spores of _Penicillium_ are capable of being transformed into yeast.[C] The interpretation of this is, that the mould _Penicillium_ may be produced from a sugar solution by "spontaneous generation," and without spore or germ of any kind. The theory is, that a molecular mass which is developed in certain solutions or infusions, may, under the influence of different circumstances, produce either animalcules or fungi. "In all these cases, no kind of animalcule or fungus is ever seen to originate from preexisting cells or larger bodies, but always from molecules."[D] The molecules are said to form small masses, which soon melt together to constitute a globular body, from which a process juts out on one side. These are the so-called _Torulæ_,[E] which give off buds which are soon transformed into jointed tubes of various diameters, terminating in rows of sporules, _Penicillium_, or capsules containing numerous globular seeds, _Aspergillus_ (_sic_).

This is but another mode of stating the same thing as above referred to by M. Trécul, that certain cells, resembling yeast cells (_Torula_), are developed spontaneously, and that these ultimately pass through the form of mould called _Penicillium_ to the more complex _Mucor_ (which the writer evidently has confounded with _Aspergillus_, unless he alludes to the ascigerous form of _Aspergillus_, long known as _Eurotium_). From what is now known of the polymorphism of fungi, there would be little difficulty in believing that cells resembling yeast cells would develop into _Penicillium_, as they do in _fact_ in what is called the "vinegar plant," and that the capsuliferous, or higher condition of this mould may be a _Mucor_, in which the sporules are produced in capsules. The difficulty arises earlier, in the supposed spontaneous origination of yeast cells from molecules, which result from the peculiar conditions of light, temperature, &c., in which certain solutions are placed. It would be impossible to review all the arguments, or tabulate all the experiments, which have been employed for and against this theory. It could not be passed over in silence, since it has been one of the stirring questions of the day. The great problem how to exclude all germs from the solutions experimented upon, and to keep them excluded, lies at the foundation of the theory. It must ever, as we think, be matter of doubt that all germs were not excluded or destroyed, rather than one of belief that forms known to be developed day by day from germs should under other conditions originate spontaneously.

Fungi are veritably and unmistakably plants, of a low organization, it is true, but still plants, developed from germs, somewhat analogous, but not wholly homologous, to the seeds of higher orders. The process of fertilization is still obscure, but facts are slowly and gradually accumulating, so that we may hope at some not very distant period to comprehend what as yet are little removed from hypotheses. Admitting that fungi are independent plants, much more complex in their relations and development than was formerly supposed, it will be expected that certain forms should be comparatively permanent, that is, that they should constitute good species. Here, also, efforts have been made to develop a theory that there are no legitimate species amongst fungi, accepting the terms as hitherto applied to flowering plants. In this, as in allied instances, too hasty generalizations have been based on a few isolated facts, without due comprehension of the true interpretation of such facts and phenomena. Polymorphism will hereafter receive special illustration, but meantime it may be well to state that, because some forms of fungi which have been described, and which have borne distinct names as autonomous species, are now proved to be only stages or conditions of other species, there is no reason for concluding that no forms are autonomous, or that fungi which appear and are developed in successive stages are not, in their entirety, good species. Instead, therefore, of insinuating that there are no good species, modern investigation tends rather to the establishment of good species, and the elimination of those that are spurious. It is chiefly amongst the microscopic species that polymorphism has been determined. In the larger and fleshy fungi nothing has been discovered which can shake our faith in the species described half a century, or more, ago. In the Agarics, for instance, the forms seem to be as permanent and as distinct as in the flowering plants. In fact, there is still no reason to dissent, except to a very limited extent, from what was written before polymorphism was accredited, that, "with a few exceptions only, it may without doubt be asserted that more certain species do not exist in any part of the organized world than amongst fungi. The same species constantly recur in the same places, and if kinds not hitherto detected present themselves, they are either such as are well known in other districts, or species which have been overlooked, and which are found on better experience to be widely diffused. There is nothing like chance about their characters or growth."[F]

The parasitism of numerous minute species on living and growing plants has its parallel even amongst phanerogams in the mistletoe and broom-rape and similar species. Amongst fungi a large number are thus parasitic, distorting, and in many cases ultimately destroying, their host, burrowing within the tissues, and causing rust and smut in corn and grasses, or even more destructive and injurious in such moulds as those of the potato disease and its allies. A still larger number of fungi are developed from decayed or decaying vegetable matter. These are found in winter on dead leaves, twigs, branches, rotten wood, the remains of herbaceous plants, and soil largely charged with disintegrated vegetables. As soon as a plant begins to decay it becomes the source of a new vegetation, which hastens its destruction, and a new cycle of life commences. In these instances, whether parasitic on living plants or developed on dead ones, the source is still vegetable. But this is not always the case, so that it cannot be predicated that fungi are wholly epiphytal. Some species are always found on animal matter, leather, horn, bone, &c., and some affect such unpromising substances as minerals, from which it would be supposed that no nourishment could be obtained, not only hard gravel stones, fragments of rock, but also metals, such as iron and lead, of which more may be said when we come to treat of the habitats of fungi. Although in general terms fungi may be described as "hysterophytal or epiphytal mycetals deriving nourishment by means of a mycelium from the matrix,"[G] there are exceptions to this rule with which the majority accord.

Of the fungi found on animal substances, none are more extraordinary than those species which attack insects. The white mould which in autumn proves so destructive to the common house-fly may for the present be omitted, as it is probably a condition of one of the _Saprolegniei_, which some authors include with fungi, and others with algæ. Wasps, spiders, moths, and butterflies become enveloped in a kind of mould named _Isaria_, which constitutes the conidia of _Torrubia_, a genus of club-shaped _Sphæriæ_ afterwards developed. Some species of _Isaria_ and _Torrubia_ also affect the larvæ and pupæ of moths and butterflies, converting the whole interior into a mass of mycelium, and fructifying in a clavate head. It has been subject for discussion whether in such instances the fungus commenced its development during the life of the insect, and thus hastened its death, or whether it resulted after death, and was subsequent to the commencement of decay.[H] The position in which certain large moths are found standing on leaves when infested with _Isaria_ resembles so closely that of the house-fly when succumbing to _Sporendonema Muscæ_, would lead to the conclusion that certainly in some cases the insect was attacked by the fungus whilst still living; whilst in the case of buried caterpillars, such as the New Zealand or British _Hepialus_, it is difficult to decide. Whether in life or death in these instances, it is clear that the silk-worm disease _Muscardine_ attacks the living insect, and causes death. In the case of the _Guêpes végétantes_, the wasp is said to fly about with the fungus partially developed.

In all fungi we may recognize a vegetative and a reproductive system: sometimes the first only becomes developed, and then the fungus is imperfect, and sometimes the latter is far more prominent than the former. There is usually an agglomeration of delicate threads, either jointed or not, which are somewhat analogous to the roots of higher plants. These delicate threads permeate the tissues of plants attacked by parasitic fungi, or they run over dead leaves forming whitened patches, formerly bearing the name of _Himantia_, but really the mycelium of some species of _Marasmius_. If checked or disturbed, the process stops here, and only a mycelium of interwoven threads is produced. In this condition the mycelium of one species so much resembles that of another, that no accurate determination can be made. If the process goes on, this mycelium gives rise to the stem and cap of an agaricoid fungus, completing the vegetative system. This in turn gives origin to a spore-bearing surface, and ultimately the fruit is formed, and then the fungus is complete; no fungus can be regarded as perfect or complete without its reproductive system being developed. In some this is very simple, in others it is as complex. In many of the moulds we have miniature representatives of higher plants in the mycelium or roots, stem, branches, and at length capsules bearing sporidia, which correspond to seeds. It is true that leaves are absent, but these are sometimes compensated by lateral processes or abortive branchlets. A tuft of mould is in miniature a forest of trees. Although such a definition may be deemed more poetic than accurate, more figurative than literal, yet few could believe in the marvellous beauty of a tuft of mould if they never saw it as exhibited under the microscope. In such a condition no doubt could be entertained of its vegetable character. But there is a lower phase in which these plants are sometimes encountered; they may consist only of single cells, or strings of cells, or threads of simple structure floating in fluids. In such conditions only the vegetative system is probably developed, and that imperfectly, yet some have ventured to give names to isolated cells, or strings of cells, or threads of mycelium, which really in themselves possess none of the elements of correct classification--the vegetative system, even, being imperfect, and consequently the reproductive is absent. As already observed, no fungus is perfect without fruit of some kind, and the peculiarities of structure and development of fruit form one of the most important elements in classification. To attempt, therefore, to give names to such imperfect fragments of undeveloped plants is almost as absurd as to name a flowering plant from a stray fragment of a root-fibril accidentally cast out of the ground--nay, even worse, for identification would probably be easier. It is well to protest at all times against attempts to push science to the verge of absurdity; and such must be the verdict upon endeavours to determine positively such incomplete organisms as floating cells, or hyaline threads which may belong to any one of fifty species of moulds, or after all to an alga. This leads us to remark, in passing, that there are forms and conditions under which fungi may be found when, fructification being absent--that is, the vegetative system alone developed--they approximate so closely to algæ that it is almost impossible to say to which group the organisms belong.

Finally, it is a great characteristic of fungi in general that they are very rapid in growth, and rapid in decay. In a night a puffball will grow prodigiously, and in the same short period a mass of paste may be covered with mould. In a few hours a gelatinous mass of _Reticularia_ will pass into a bladder of dust, or a _Coprinus_ will be dripping into decay. Remembering this, mycophagists will take note that a fleshy fungus which may be good eating at noon may undergo such changes in a few hours as to be anything but good eating at night. Many instances have been recorded of the rapidity of growth in fungi; it may also be accepted as an axiom that they are, in many instances, equally as rapid in decay.

The affinity between lichens and fungi has long been recognized to its full and legitimate extent by lichenologists and mycologists.[I] In the "Introduction to Cryptogamic Botany," it was proposed to unite them in one alliance, under the name of _Mycetales_, in the same manner as the late Dr. Lindley had united allied orders under alliances in his "Vegetable Kingdom;" but, beyond this, there was no predisposition towards the theory since propounded, and which, like all new theories, has collected a small but zealous circle of adherents. It will be necessary briefly to summarize this theory and the arguments by which it is supported and opposed, inasmuch as it is intimately connected with our subject.

As recently as 1868, Professor Schwendener first propounded his views,[J] and then briefly and vaguely, that all and every individual lichen was but an algal, which had collected about it a parasitic fungal growth, and that those peculiar bodies which, under the name of _gonidia_, were considered as special organs of lichens, were only imprisoned algæ. In language which the Rev. J. M. Crombie[K] describes as "pictorial," this author gave the general conclusion at which he had arrived, as follows:--"As the result of my researches, all these growths are not simple plants, not individuals in the usual sense of the term; they are rather colonies, which consist of hundreds and thousands of individuals, of which, however, only one acts as master, while the others, in perpetual captivity, provide nourishment for themselves and their master. This master is a fungus of the order _Ascomycetes_, a parasite which is accustomed to live upon the work of others; its slaves are green algæ, which it has sought out, or indeed caught hold of, and forced into its service. It surrounds them, as a spider does its prey, with a fibrous net of narrow meshes, which is gradually converted into an impenetrable covering. While, however, the spider sucks its prey and leaves it lying dead, the fungus incites the algæ taken in its net to more rapid activity; nay, to more vigorous increase." This hypothesis, ushered upon the world with all the prestige of the Professor's name, was not long in meeting with adherents, and the cardinal points insisted upon were--1st. That the generic relationship of the coloured "gonidia" to the colourless filaments which compose the lichen thallus, had only been assumed, and not proved; 2nd. That the membrane of the gonidia was chemically different from the membrane of the other tissues, inasmuch as the first had a reaction corresponding to that of algæ, whilst the second had that of fungi; 3rd. That the different forms and varieties of gonidia corresponded with parallel types of algæ; 4th. That as the germination of the spore had not been followed further than the development of a hypothallus, it might be accounted for by the absence of the essential algal on which the new organism should become parasitic; 5th. That there is a striking correspondence between the development of the fruit in lichens and in some of the sporidiiferous fungi (_Pyrenomycetes_).

These five points have been combated incessantly by lichenologists, who would really be supposed by ordinary minds to be the most practically acquainted with the structure and development of these plants, in opposition to the theorists. It is a fact which should have some weight, that no lichenologist of repute has as yet accepted the theory. In 1873 Dr. E. Bornet[L] came to the aid of Schwendener, and almost exhausted the subject, but failed to convince either the practised lichenologist or mycologist. The two great points sought to be established are these, that what we call lichens are compound organisms, not simple, independent vegetable entities; and that this compound organism consists of unicellular algæ, with a fungus parasitic upon them. The coloured gonidia which are found in the substance, or thallus of lichens, are the supposed algæ; and the cellular structure which surrounds, encloses, and imprisons the gonidia is the parasitic fungus, which is parasitic on something infinitely smaller than itself, and which it entirely and absolutely isolates from all external influences.

Dr. Bornet believed himself to have established that every gonidium of a lichen may be referred to a species of algæ, and that the connection between the hypha and gonidia is of such a nature as to exclude all possibility of the one organ being produced by the other. This he thinks is the only way in which it can be accounted for that the gonidia of diverse lichens should be almost identical.

Dr. Nylander, in referring to this hypothesis of an imprisoned algal,[M] writes: "The absurdity of such an hypothesis is evident from the very consideration that it cannot be the case that an organ (gonidia) should at the same time be a parasite on the body of which it exercises vital functions; for with equal propriety it might be contended that the liver or the spleen constitutes parasites of the mammiferæ. Parasite existence is autonomous, living upon a foreign body, of which nature prohibits it from being at the same time an organ. This is an elementary axiom of general physiology. But observation directly made teaches that the green matter originally arises within the primary chlorophyll- or phycochrom-bearing cellule, and consequently is not intruded from any external quarter, nor arises in any way from any parasitism of any kind. The cellule at first is observed to be empty, and then, by the aid of secretion, green matter is gradually produced in the cavity and assumes a definite form. It can, therefore, be very easily and evidently demonstrated that the origin of green matter in lichens is entirely the same as in other plants." On another occasion, and in another place, the same eminent lichenologist remarks,[N] as to the supposed algoid nature of gonidia--"that such an unnatural existence as they would thus pass, enclosed in a prison and deprived of all autonomous liberty, is not at all consonant with the manner of existence of the other algæ, and that it has no parallel in nature, for nothing physiologically analogous occurs anywhere else. Krempelhuber has argued that there are no conclusive reasons against the assumption that the lichen-gonidia may be self-developed organs of the lichen proper rather than algæ, and that these gonidia can continue to vegetate separately, and so be mistaken for unicellular algæ." In this Th. Fries seems substantially to concur. But there is one strong argument, or rather a repetition of an argument already cited, placed in a much stronger light, which is employed by Nylander in the following words:--"So far are what are called algæ, according to the turbid hypothesis of Schwendener, from constituting true algæ, that on the contrary it may be affirmed that they have a lichenose nature, whence it follows that these pseudo-algæ are in a systematic arrangement to be referred rather to the lichens, and that the class of algæ hitherto so vaguely limited should be circumscribed by new and truer limits."

As to another phase in this question, there are, as Krempelhuber remarks, species of lichens which in many countries do not fructify, and whose propagation can only be carried on by means of the soredia, and the hyphæ of such could in themselves alone no more serve for propagation than the hyphæ from the pileus or stalk of an Agaric, while it is highly improbable that they could acquire this faculty by interposition of a foreign algal. On the other hand he argues: "It is much more conformable to nature that the gonidia, as self-developed organs of the lichens, should, like the spores, enable the hyphæ proceeding from them to propagate the individual."[O]

A case in point has been adduced[P] in which gonidia were produced by the hypha, and the genus _Emericella_,[Q] which is allied to _Husseia_ in the _Trichogastres_, shows a structure in the stem exactly resembling _Palmella botryoides_ of Greville, and to what occurs in _Synalyssa_. _Emericella_, with one or two other genera, must, however, be considered as connecting _Trichogastres_ with lichens, and the question cannot be considered as satisfactorily decided till a series of experiments has been made on the germination of lichen spores and their relation to free algæ considered identical with gonidia. Mr. Thwaites was the first to point out[R] the relation of the gonidia in the different sections of lichens to different types of supposed algæ. The question cannot be settled by mere _à priori_ notions. It is, perhaps, worthy of remark that in _Chionyphe Carteri_ the threads grow over the cysts exactly as the hypha of lichens is represented as growing over the gonidia.

Recently, Dr. Thwaites has communicated his views on one phase of this controversy,[S] which will serve to illustrate the question as seen from the mycological side. As is well known, this writer has had considerable experience in the study of the anatomy and physiology of all the lower cryptogamia, and any suggestion of his on such a subject will at least commend itself to a patient consideration.

"According to our experience," he writes, "I think parasitic fungi invariably produce a sad effect upon the tissues they fix themselves upon or in. These tissues become pale in colour, and in every respect sickly in appearance. But who has ever seen the gonidia of lichens the worse for having the 'hypha' growing amongst them? These gonidia are always in the plumpest state, and with the freshest, healthiest colour possible. Cannot it enter into the heads of these most patient and excellent observers, that a cryptogamic plant may have two kinds of tissue growing side by side, without the necessity of one being parasitic upon the other, just as one of the higher plants may have half a dozen kinds of tissue making up its organization? The beautifully symmetrical growth of the same lichens has seemed to me a sufficient argument against one portion being parasitic upon another, but when we see all harmony and robust health, the idea that one portion is subsisting parasitically upon another appears to me to be a perfect absurdity."

It appears to us that a great deal of confusion and a large number of errors which creep into our modern generalizations and hypotheses, may be traced to the acceptance of analogies for identities. How many cases of mistaken identity has the improvement of microscopes revealed during the past quarter of a century. This should at least serve as a caution for the future.

Apart, however, from the "gonidia," whatever they may be, is the remainder of the lichen a genuine fungus? Nylander writes, "The anatomical filamentose elements of lichens are distinguished by various characters from the hyphæ of fungi. They are firmer, elastic, and at once present themselves in the texture of lichens. On the other hand, the hyphæ of fungi are very soft, they possess a thin wall, and are not at all gelatinous, while they are immediately dissolved by the application of hydrate of potash, &c."[T]

Our own experience is somewhat to the effect, that there are some few lichens which are doubtful as to whether they are fungi or lichens, but, in by far the majority of cases, there is not the slightest difficulty in determining, from the peculiar firmness and elasticity of the tissues, minute peculiarities which the practised hand can detect rather than describe, and even the general character of the fruit that they differ materially from, though closely allied to fungi. We have only experience to guide us in these matters, but that is something, and we have no experience in fungi of anything like a _Cladonia_, however much it may resemble a _Torrubia_ or _Clavaria_. We have _Pezizæ_ with a subiculum in the section _Tapesia_, but the veriest tyro would not confound them with species of _Parmelia_. It is true that a great number of lichens, at first sight, and casually, resemble species of the _Hysteriacei_, but it is no less strange than true, that lichenologists and mycologists know their own sufficiently not to commit depredations on each other.

Contributions are daily being made to this controversy, and already the principal arguments on both sides have appeared in an English dress,[U] hence it will be unnecessary to repeat those which are modifications only of the views already stated, our own conclusions being capable of a very brief summary: that lichens and fungi are closely related the one to the other, but that they are not identical; that the "gonidia" of lichens are part of the lichen-organization, and consequently are not algæ, or any introduced bodies; that there is no parasitism; and that the lichen thallus, exclusive of gonidia, is wholly unknown amongst fungi.

The Rev. J. M. Crombie has therefore our sympathies in the remark with which his summary of the gonidia controversy closes, in which he characterizes it as a "sensational romance of lichenology," of the "unnatural union between a captive algal damsel and a tyrant fungal master."

[A] De Bary, "Des Myxomycètes," in "Ann. des Sci. Nat." 4 sér. xi. p.
153; "Bot. Zeit." xvi. p. 357. De Bary's views are controverted
by M. Wigand in "Ann. des Sci. Nat." 4 sér. (Bot.) xvi. p. 255,
&c.

[B] De Bary, "Recherches sur le Developpement de quelques Champignons
Parasites," in "Ann. des Sci. Nat." 4 sér. (Bot.) xx. p. 5.

[C] "Popular Science Review," vol. viii. p. 96.

[D] Dr. J. H. Bennett "On the Molecular Origin of Infusoria," p. 56.

[E] They have, however, no close relation with real _Torulæ_, such as
_T. monilioides_, &c.--COOKE'S _Handbook_, p. 477.

[F] Berkeley's "Outlines of British Fungology," p. 24.

[G] Berkeley's "Introduction to Cryptogamic Botany," p. 235.

[H] Gray, "Notices of Insects which form the Basis of Fungoid
Parasites."

[I] On the relation or connection between fungi and lichens, H. C.
Sorby has some pertinent remarks in his communication to the
Royal Society on "Comparative Vegetable Chromatology"
(Proceedings Royal Society, vol. xxi. 1873, p. 479), as one
result of his spectroscopic examinations. He says, "Such being
the relations between the organs of reproduction and the
foliage, it is to some extent possible to understand the
connection between parasitic plants like fungi, which do not
derive their support from the constructive energy of their
fronds, and those which are self-supporting and possess true
fronds. In the highest classes of plants the flowers are
connected with the leaves, more especially by means of
xanthophyll and yellow xanthophyll, whereas in the case of
lichens the apothecia contain very little, if any, of those
substances, but a large amount of the lichenoxanthines so
characteristic of the class. Looking upon fungi from this
chromatological point of view, they bear something like the
same relation to lichens that the petals of a leafless
parasitic plant would bear to the foliage of one of normal
character--that is to say, they are, as it were, the coloured
organs of reproduction of parasitic plants of a type closely
approaching that of lichens, which, of course, is in very
close, if not in absolute agreement with the conclusions drawn
by botanists from entirely different data."

[J] Schwendener, "Untersuchungen über den Flechtenthallus."

[K] Crombie (J. M.) "On the Lichen-Gonidia Question," in "Popular
Science Review" for July, 1874.

[L] Bornet, (E.), "Recherches sur les Gonidies des Lichens," in "Ann.
des Sci. Nat." 1873, 5 sér. vol. xvii.

[M] Nylander, "On the Algo-Lichen Hypothesis," &c., in "Grevillea,"
vol. ii. (1874), No. 22, p. 146.

[N] In Regensburg "Flora," 1870, p. 92.

[O] Rev. J. M. Crombie, in "Popular Science Review," July, 1874.

[P] Berkeley's "Introduction to Cryptogamic Botany," p. 373, fig.
78_a._

[Q] Berkeley's "Introduction," p. 341, fig. 76.

[R] "Annals and Magazine of Natural History," April, 1849.

[S] In "Gardener's Chronicle" for 1873, p. 1341.

[T] "Grevillea," vol ii. p. 147, in note.

[U] W. Archer, in "Quart. Journ. Micr. Sci." vol. xiii. p. 217; vol.
xiv. p. 115. Translation of Schwendener's "Nature of the
Gonidia of Lichens," in same journal, vol. xiii. p. 235.

II.

STRUCTURE.

Without some knowledge of the structure of fungi, it is scarcely possible to comprehend the principles of classification, or to appreciate the curious phenomena of polymorphism. Yet there is so great a variety in the structure of the different groups, that this subject cannot be compressed within a few paragraphs, neither do we think that this would be desired if practicable, seeing that the anatomy and physiology of plants is, in itself, sufficiently important and interesting to warrant a rather extended and explicit survey. In order to impart as much practical utility as possible to this chapter, it seems advisable to treat some of the most important and typical orders and suborders separately, giving prominence to the features which are chiefly characteristic of those sections, following the order of systematists as much as possible, whilst endeavouring to render each section independent to a considerable extent, and complete in itself. Some groups naturally present more noteworthy features than others, and will consequently seem to receive more than their proportional share of attention, but this seeming inequality could scarcely have been avoided, inasmuch as hitherto some groups have been more closely investigated than others, are more intimately associated with other questions, or are more readily and satisfactorily examined under different aspects of their life-history.

AGARICINI.--For the structure that prevails in the order to which the mushroom belongs, an examination of that species will be almost sufficient. Here we shall at once recognize three distinct parts requiring elucidation, viz. the rooting slender fibres that traverse the soil, and termed the _mycelium_, or spawn, the stem and cap or pileus, which together constitute what is called the _hymenophore_, and the plates or gills on the under surface of the cap, which bear the _hymenium_. The earliest condition in which the mushroom can be recognized as a vegetable entity is in that of the "spawn" or mycelium, which is essentially an agglomeration of vegetating spores. Its normal form is that of branched, slender, entangled, anastomosing, hyaline threads. At certain privileged points of the mycelium, the threads seem to be aggregated, and become centres of vertical extension. At first only a small nearly globose budding, like a grain of mustard seed, is visible, but this afterwards increases rapidly, and other similar buddings or swellings appear at the base.[A] These are the young hymenophore. As it pushes through the soil, it gradually loses its globose form, becomes more or less elongated, and in this condition a longitudinal section shows the position of the future gills in a pair of opposite crescent-shaped darker-coloured spots near the apex. The dermal membrane, or outer skin, seems to be continuous over the stem and the globose head. At present, there is no external evidence of an expanded pileus and gills; a longitudinal section at this stage shows that the gills are being developed, that the pileus is assuming its cap-like form, that the membrane stretching from the stem to the edge of the young pileus is separating from the edge of the gills, and forming a _veil_, which, in course of time, will separate below and leave the gills exposed. When, therefore, the mushroom has arrived almost at maturity, the pileus expands, and in this act the veil is torn away from the margin of the cap, and remains for a time like a collar around the stem. Fragments of the veil often remain attached to the margin of the pileus, and the collar adherent to the stem falls back, and thenceforth is known as the _annulus_ or ring. We have in this stage the fully-developed hymenophore,--the stem with its ring, supporting an expanded cap or pileus, with gills on the under surface bearing the hymenium.[B] A longitudinal section cut through the pileus and down the stem, gives the best notion of the arrangement of the parts, and their relation to the whole. By this means it will be seen that the pileus is continuous with the stem, that the substance of the pileus descends into the gills, and that relatively the substance of the stem is more fibrous than that of the pileus. In the common mushroom the ring is very distinct surrounding the stem, a little above the middle, like a collar. In some Agarics the ring is very fugacious, or absent altogether. The form of the gills, their mode of attachment to the stem, their colour, and more especially the colour of the spores, are all very important features to be attended to in the discrimination of species, since they vary in different species. The whole substance of the Agaric is cellular. A longitudinal slice from the stem will exhibit under the microscope delicate tubular cells, the general direction of which is lengthwise, with lateral branches, the whole interlacing so intimately that it is difficult to trace any individual thread very far in its course. It will be evident that the structure is less compact as it approaches the centre of the stem, which in many species is hollow. The _hymenium_ is the spore-bearing surface, which is exposed or naked, and spread over the gills. These plates are covered on all sides with a delicate membrane, upon which the reproductive organs are developed. If it were possible to remove this membrane in one entire piece and spread it out flat, it would cover an immense surface, as compared with the size of the pileus, for it is plaited or folded like a lady's fan over the whole of the gill-plates, or lamellæ, of the fungus.[C] If the stem of a mushroom be cut off close to the gills, and the cap laid upon a sheet of paper, with the gills downwards, and left there for a few hours, when removed a number of dark radiating lines will be deposited upon the paper, each line corresponding with the interstices between one pair of gills. These lines are made up of spores which have fallen from the hymenium, and, if placed under the microscope, their character will at once be made evident. If a fragment of the hymenium be also submitted to a similar examination, it will be found that the whole surface is studded with spores. The first peculiarity which will be observed is, that these spores are almost uniformly in groups of four together. The next feature to be observed is, that each spore is borne upon a slender stalk or sterigma, and that four of these sterigmata proceed from the apex of a thicker projection, from the hymenium, called a _basidium_, each basidium being the supporter of four sterigmata, and each sterigma of a spore.[D] A closer examination of the hymenium will reveal the fact that the basidia are accompanied by other bodies, often larger, but without sterigmata or spores; these have been termed _cystidia_, and their structure and functions have been the subject of much controversy.[E] Both kinds of bodies are produced on the hymenium of most, if not all, the Agaricini.

The basidia are usually expanded upwards, so as to have more or less of a clavate form, surmounted by four slender points, or tubular processes, each supporting a spore; the contents of these cells are granular, mixed apparently with oleaginous particles, which communicate through the slender tubes of the spicules with the interior of the spores. Corda states that, although only one spore is produced at a time on each sporophore, when this falls away others are produced in succession for a limited period. As the spores approach maturity, the connection between their contents and the contents of the basidia diminishes and ultimately ceases. When the basidium which bears mature spores is still well charged with granular matter, it may be presumed that the production of a second or third series of spores is quite possible. Basidia exhausted entirely of their contents, and which have become quite hyaline, may often be observed.

The cystidia are usually larger than the basidia, varying in size and form in different species. They present the appearance of large sterile cells, attenuated upwards, sometimes into a slender neck. Corda was of opinion that these were male organs, and gave them the name of _pollinaires_. Hoffmann has also described[F] both these organs under the names of _pollinaria_ and _spermatia_, but does not appear to recognize in them the sexual elements which those names would indicate; whilst de Seynes suggests that the cystidia are only organs returned to vegetative functions by a sort of hypertrophy of the basidia.[G] This view seems to be supported by the fact that, in the section _Pluteus_ and some others, the cystidia are surmounted by short horns resembling sterigmata. Hoffmann has also indicated[H] the passage of cystidia into basidia. The evidence seems to be in favour of regarding the cystidia as barren conditions of basidia. There are to be found upon the hymenium of Agarics a third kind of elongated cells, called by Corda[I] basilary cells, and by Hoffmann "sterile cells," which are either equal in size or smaller than the basidia, with which also their structure agrees, excepting in the development of spicules. These are the "proper cells of the hymenium" of Léveillé, and are simply the terminal cells of the gill structure--cells which, under vigorous conditions, might be developed into basidia, but which are commonly arrested in their development. As suggested by de Seynes, the hymenium seems to be reduced to great simplicity, "one sole and self-same organ is the basis of it; according as it experiences an arrest of development, as it grows and fructifies, or as it becomes hypertrophied, it gives us a paraphyse, a basidium, or a cystidium--in other terms, atrophied basidium, normal basidium and hypertrophied basidium; these are the three elements which form the hymenium."[J]

The only reproductive organs hitherto demonstrated in Agarics are the spores, or, as sometimes called, from their method of production, _basidiospores_.[K] These are at first colourless, but afterwards acquire the colour peculiar to the species. In size and form they are, within certain limits, exceedingly variable, although form and size are tolerably constant in the same species. At first all are globose; as they mature, the majority are ovoid or elliptic; some are fusiform, with regularly attenuated extremities. In _Hygrophorus_ they are rather irregular, reniform, or compressed in the middle. Sometimes the external surface is rough with more or less projecting warts. Some mycologists are of opinion that the covering of the spore is double, consisting of an _exospore_ and an _endospore_, the latter being very fine and delicate. In other orders the double coating of the spore has been demonstrated. When the spore is coloured, the external membrane alone appears to possess colour, the endospore being constantly hyaline. It may be added here, that in this order the spore is simple and unicellular. In _Lactarius_ and _Russula_ the trama, or inner substance, is vesicular. True latex vessels occur occasionally in _Agaricus_, though not filled with milk as in _Lactarius_.

POLYPOREI.--In this order the gill plates are replaced by tubes or pores, the interior of which is lined by the hymenium; indications of this structure having already been exhibited in some of the lower _Agaricini._ In many cases the stem is suppressed. The substance is fleshy in _Boletus_, but in _Polyporus_ the greater number of species are leathery or corky, and more persistent. The basidia, spicules, and quaternate spores agree with those of _Agaricini_.[L] In fact there are no features of importance which relate to the hymenium in any order of _Hymenomycetes_ (the _Tremellini_ excepted) differing from the same organ in _Agaricini_, unless it be the absence of _cystidia_.

HYDNEI.--Instead of pores, in this order the hymenium is spread over the surface of spines, prickles, or warts.[M]

AURICULARINI.--The hymenium is more or less even, and in--

CLAVARIEI the whole fungus is club-shaped, or more or less intricately branched, with the hymenium covering the outer surface.

TREMELLINI.--In this order we have a great departure from the character of the substance, external appearance, and internal structure of the other orders in this family. Here we have a gelatinous substance, and the form is lobed, folded, convolute, often resembling the brain of some animal. The internal structure has been specially illustrated by M. Tulasne,[N] through the common species, _Tremella mesenterica_. This latter is of a fine golden yellow colour, and rather large size. It is uniformly composed throughout of a colourless mucilage, with no appreciable texture, in which are distributed very fine, diversely branched and anastomosing filaments. Towards the surface, the ultimate branches of this filamentous network give birth, both at their summits and laterally, to globular cells, which acquire a comparatively large size. These cells are filled with a protoplasm, to which the plant owes its orange colour. When they have attained their normal dimensions, they elongate at the summit into two, three, or four distinct, thick, obtuse tubes, into which the protoplasm gradually passes. The development of these tubes is unequal and not simultaneous, so that one will often attain its full dimensions, equal, perhaps, to three or four times the diameter of the generative cell, whilst the others are only just appearing. By degrees, as each tube attains its full size, it is attenuated into a fine point, the extremity of which swells into a spheroidal cell, which ultimately becomes a spore. Sometimes these tubes, or spicules, send out one or two lateral branches, each terminated by a spore. These spores (about ·006 to ·008 _mm._ diameter) are smooth, and deposit themselves, like a fine white dust, on the surface of the _Tremella_ and on its matrix. M. Léveillé[O] was of opinion that the basidia of the Tremellini were monosporous, whilst M. Tulasne has demonstrated that they are habitually tetrasporous, as in other of the Hymenomycetes. Although agreeing in this, they differ in other features, especially in the globose form of the basidia, mode of production of the spicules, and, finally, the division of the basidia into two, three, or four cells by septa which cut each other in their axis. This division precedes the growth of the spicules. It is not rare to see these cells, formed at the expense of an unilocular basidium, become partly isolated from each other; in certain cases they seem to have separated very early, they then become larger than usual, and are grouped on the same filament so as to represent a kind of buds. This phenomenon usually takes place below the level of the fertile cells, at a certain depth in the mucous tissue of the _Tremella_.

Besides the reproductive system here described, Tulasne also made known the existence of a series of filaments which produce spermatia. These filaments are often scattered and confused with those which produce the basidia, and not distinguishable from them in size or any other apparent characteristic, except the manner in which their extremities are branched in order to produce the spermatia. At other times the spermatia-bearing surface covers exclusively certain portions of the fungus, especially the inferior lobes, imparting thereto a very bright orange colour, which is communicated by the layer of spermatia, unmixed with spores. These spots retain their bright colour, while the remainder of the plant becomes pale, or covered with a white dust. The spermatia are very small, spherical, and smooth, scarcely equalling ·002 _mm._ They are sessile, sometimes solitary, sometimes three or four together, on the slightly swollen extremities of certain filaments of the weft of the fungus.[P] Tulasne found it impossible to make these corpuscles germinate, and in all essential particulars they agreed with the spermatia found in ascomycetous fungi.