Chapter III: The Algæ

BY A. W. WILLS.

The great class of Algæ includes the sea-weeds, together with a large number of plants, mostly of microscopic size and of simple cellular structure, which abound wherever fresh water is found, whether in the form of running streams or stagnant pools, or even as covering damp surfaces of ground.

A broad subdivision of the Algæ into three groups has been generally accepted by botanists, these being the Rhodosporeæ (red-spored), Melanosporeæ (dark-spored), and Chlorosporeæ (green-spored). The marine genera are distributed over all three of these groups; the freshwater ones belong almost exclusively to the last. The classification of the freshwater Chlorosperms is by no means satisfactory, but it is impossible to discuss it within the limits of this article.

It is to be regretted that scarcely any of the botanists of Birmingham have made the Algæ their special study; hence the information at our disposal is insufficient to enable us to group the recorded species with reference to their occurrence in the several adjacent counties. This is, however, the less important because the distribution of this class of plants is not dependent, to the same extent as that of Phænogams, either on climate or soil, though it is probably not altogether independent of either. Their abundance, therefore, is in pretty direct proportion to that of such spaces of water as afford favourable conditions for their growth.

Hence, as the neighbourhood of Birmingham is mostly characterised by light and porous soils, the habitats in which Algæ are to be found are somewhat restricted. There are, however, two conspicuous exceptions. The tract of land about seven miles from Birmingham, known as Sutton Park, embraces a singular variety of scenery and presents conditions highly favourable to algoid growth in the shape of clear springs and streams, large sheets of water, and a considerable area of peaty bogs. Again, the mining district of South Staffordshire and Worcestershire, popularly known as the Black Country, affords among its pit-banks a great number of pools which are seldom dried up even in the hottest summer, and many of which are partially fed by water from adjacent mines or engines. Their number has been much diminished during the last few years by the operations of the South Staffordshire Mines Drainage Commission, but is still very large and these constitute a rich hunting ground to the student of freshwater Algæ.

The brief notes which follow must be regarded merely as an indication of the general character of this branch of the Midland Flora. Any attempt systematically to enumerate the recorded species would far exceed the necessary limits of this notice.

The great group of so-called Unicellular Algæ is universally distributed, and the familiar forms included under the ill-defined genera of Pleurococcus, Glœocystis, Tetraspora, Pediastrum, &c., are found abundantly in this district wherever conditions favourable to their growth are present. Among these low forms may be mentioned _Apiocystis Brauniana_, parasitic on larger Algæ in stagnant pools; the extremely rare _Mischococcus confervicola_, recorded as found near Stafford, and _Polyedrium tetrahedricum_ found on decaying leaves in a small pit near Sutton. _Ophiocytium cochleare_, until lately regarded as a very scarce plant, is not uncommon in similar habitats.

The remarkable _Hydrodictyon utriculatum_, popularly known as “Water Net,” appeared some years ago in Blackroot Pool, Sutton Park, in enormous quantities, but shortly disappeared and has not been seen there since. It has also been recorded by Mr. T. Bolton as found in Bourne Pool, near Aldridge.

The large tribe of Volvocineæ is represented by the well-known forms of Gonium, Pandorina, and Eudorina, and by the typical _Volvox globator_, which, as is its wont, occasionally appears in some of the pools of the district in great profusion, only to vanish as capriciously. Mr. Bolton has recorded the rare and interesting _Volvox globator_ ♂,--the _Sphærosira volvox_ of Ehrenberg--as occurring in the small pool in the gravel pit near Blackroot Pool, Sutton Park.

Passing to the Zygnemaceæ, Vaucheriaceæ and other filamentous Algæ, we find a large number of species of Zygnema, Spirogyra, Zygogonium, Mesocarpus, Staurocarpus, Vaucheria, &c., occupying ditches, small pools and other stagnant waters; it is scarcely possible to take a bottleful of water from these stations in summer and autumn without finding examples of the curious modes of reproduction characteristic of these genera.

In running streams and in the still ponds of the district the long fronds of Enteromorpha, the dense tresses of brilliant green Cladophoræ and the graceful tufts of Stigeoclonium and Chætophora abound. The exquisite _Cœtophora endiviæfolia_ reappears at intervals in Keeper’s Pool, Sutton Park; this species has also been found by Mr. Bolton in an old gravel pit at Hill Hook and in Earlswood reservoir.

The elegant _Bulbochœte setigera_ is met with in small fragments in stagnant pools, and the singular _Coleochœte scutata_ is to be found adherent to submerged water weeds.

The tepid waters of the South Staffordshire coal district are specially favourable to the growth of Oscillatorieæ, which form on their margins immense sheets of the deepest green velvet.

Several species of Batrachospermum (among which _B. atrum_ is locally the rarest, having been found at Halesowen only) occur in small masses in clear streams, but they must be regarded as somewhat scarce plants. _Lemania fluviatilis_ should be mentioned as common in the Avon and Severn, and the very rare _Bangia atropurpurea_ as occurring on a water wheel in the former river at Stratford-on-Avon, although these habitats are somewhat beyond the limits contemplated in this sketch.

The Diatomaceæ of the neighbourhood do not appear to have been the objects of systematic study, and the only species of special interest which we remember to have found is the wonderful _Bacillaria paradoxa_, well known as a remarkable microscopic object from the strange manner in which its linear frustules glide over one another, so that the whole plant is incessantly assuming a different form. It has been found by Mr. Bolton, along with many other species, in a disused arm of the canal near Albion Station, and by the writer in a small stream near the same spot. A careful search would doubtless result in the discovery of a large number of representative species of this class.

In conclusion, we turn for a moment to the very beautiful tribe of Desmidieæ, and, although the district by no means abounds in the peaty bogs which are their especial haunts, a goodly list of ordinary species has been recorded. Sutton Park is the best locality for these plants, and in addition to the commoner forms of Micrasterias, Euastrum, Closterium, &c., which are here found in abundance, this habitat has yielded many rare and several new species, among which the following are worthy of special notice, viz.:--_Micrasterias papillifera_, _M. Cruxmelitensis_, _M. angulosa_, _M. denticulata_, var. _lichmoides_, and _M. Americana, forma major_; _Cosmarium coronatum_, _Closterium directum_, _Cl. angustatum_, and _Cl. Pritchardianum_; _Penium closteriodes_, _P. Jenneri_, and _P. Nägeli_.

A more detailed list of species is inadmissible, but the foregoing brief sketch will suffice to show that the Freshwater Algæ of the neighbourhood are tolerably abundant, and by no means devoid of interest.