Chapter III: Introduction

Thoreau tells us, "Nature made a fern for pure leaves." Fern leaves are in the highest order of cryptogams. Like those of flowering plants they are reinforced by woody fibres running through their stems, keeping them erect while permitting graceful curves. Their exquisite symmetry of form, their frequent finely cut borders, and their rich shades of green combine to make them objects of rare beauty; while their unique vernation and method of fruiting along with their wonderful mystery of reproduction invest them with marked scientific interest affording stimulus and culture to the thoughtful mind. By peculiar enchantments these charming plants allure the ardent Nature-lover to observe their haunts and habits.

"Oh, then most gracefully they wave
In the forest, like a sea,
And dear as they are beautiful
Are these fern leaves to me."

As a rule the larger and coarser ferns grow in moist, shady situations, as swamps, ravines, and damp woods; while the smaller ones are more apt to be found along mountain ranges in some dry and even exposed locality. A tiny crevice in some high cliff is not infrequently chosen by these fascinating little plants, which protect themselves from drought by assuming a mantle of light wool, or of hair and chaff, with, perhaps, a covering of white powder as in some cloak ferns--thus keeping a layer of moist air next to the surface of the leaf, and checking transpiration.

Some of the rock-loving ferns in dry places are known as "resurrection" ferns, reviving after their leaves have turned sere and brown. A touch of rain, and lo! they are green and flourishing.

Ferns vary in height from the diminutive filmy fern of less than an inch to the vast tree ferns of the tropics, reaching a height of sixty feet or more.

REPRODUCTION

Ferns are propagated in various ways. A frequent method is by perennial rootstocks, which often creep beneath the surface, sending up, it may be, single fronds, as in the common bracken, or graceful leaf-crowns, as in the cinnamon fern. The bladder fern is propagated in part from its bulblets, while the walking leaf bends over to the earth and roots at the tip.

Ferns are also reproduced by spores, a process mysterious and marvellous as a fairy tale. Instead of seeds the fern produces spores, which are little one-celled bodies without an embryo and may be likened to buds. A spore falls upon damp soil and germinates, producing a small, green, shield-shaped patch much smaller than a dime, which is called a prothállium (or prothallus). On its under surface delicate root hairs grow to give it stability and nutriment; also two sorts of reproductive organs known as antherídia and archegònia, the male and female growths analogous to the stamens and pistils in flowers. From the former spring small, active, spiral bodies called ántherozòids, which lash about in the moisture of the prothállium until they find the archegònia, the cells of which are so arranged in each case as to form a tube around the central cell, which is called the òösphere, or egg-cell, the point to be fertilized. When one of the entering ántherozòids reaches this point the desired change is effected, and the canal of the archegònium closes. The empty òösphere becomes the quickened òösphore whose newly begotten plant germ unfolds normally by the multiplication of cells that become, in turn, root, stem, first leaf, etc., while the prothállium no longer needed to sustain its offspring withers away.[1]

[Footnote 1: In the accompanying illustration, it should be remembered that the reproductive parts of a fern are microscopic and cannot be seen by the naked eye.]

Fern plants have been known to spring directly from the prothállus by a budding process apart from the organs of fertilization, showing that Nature "fulfills herself in many ways."[2]

[Footnote 2: The scientific term for this method of reproduction is apógamy (apart from marriage). Sometimes the prothallus itself buds directly from the frond without spores, for which process the term apóspory is used. (Meaning, literally, without spores.)]

VERNATION

All true ferns come out of the ground head foremost, coiled up like a watch-spring, and are designated as "fiddle-heads," or crosiers. (A real crosier is a bishop's staff.) Some of these odd young growths are covered with "fern wool," which birds often use in lining their nests. This wool usually disappears later as the crosier unfolds into the broad green blade. The development of plant shoots from the bud is called vernation (Latin, _ver_ meaning spring), and this unique uncoiling of ferns, "circinnate vernation."

VEINS

The veins of a fern are free, when, branching from the mid-vein, they do not connect with each other, and simple when they do not fork. When the veins intersect they are said to anastomose (Greek, an opening, or network), and their meshes are called arèolæ or áreoles (Latin, _areola_, a little open space).

EXPLANATION OF TERMS

A frond is said to be pinnate (Latin, _pinna_, a feather), when its primary divisions extend to the rachis, as in the Christmas fern (Fig. 1). A frond is bipinnate (Latin, _bis_, twice) when the lobes of the pinnæ extend to the midvein as in the royal fern (Fig. 2). These divisions of the pinnæ are called pinnules. When a frond is tripínnate the last complete divisions are called ultimate pinnules or segments. A frond is pinnátifid when its lobes extend halfway or more to the rachis or midvein as in the middle lobes of the pinnátifid spleenwort (Fig. 3). The pinnæ of a frond are often pinnátifid when the frond itself is pinnate; and a frond may be pinnate in its lower part and become pinnátifid higher up as in the pinnátifid spleenwort just mentioned (Fig. 3).

The divisions of a pinnátifid leaf are called segments; of a bipinnátifid or tripinnátifid leaf, ultimate segments.

SPORÁNGIA AND FRUIT DOTS

Fern spores are formed in little sacs known as spore-cases or sporángia (Fig. 4). They are usually clustered in dots or lines on the back or margin of a frond, either on or at the end of a small vein, or in spike-like racemes on separate stalks. Sori (singular _sorus_, a heap), or fruit dots may be naked as in the polypody, but are usually covered with a thin, delicate membrane, known as the indusium (Greek, a dress, or mantle). The family or genus of a fern is often determined by the shape of its indusium; e.g., the indusium of the woodsias is star-shaped; of the Dicksonias, cup-shaped; of the aspleniums, linear; of the wood ferns, kidney-shaped, etc.

In many ferns the sporangia are surrounded in whole or in part by a vertical, elastic ring (annulus) reminding one of a small, brown worm closely coiled (Fig. 4). As the spores mature, the ring contracts and bursts with considerable force, scattering the spores. The spores of the different genera mature at different times from May to September. A good time to collect ferns is just before the fruiting season. (For times of fruiting see individual descriptions or chronological chart on page 220.)

HELPFUL HINTS

The following hints may be helpful to the young collector:

1. A good lens with needles for dissecting is very helpful in examining the sori, veins, glands, etc., as an accurate knowledge of any one of these items may aid in identifying a given specimen. Bausch and Lomb make a convenient two-bladed pocket glass for about two dollars.[1]

[Footnote 1: In the linen tester here figured (cost $1.50) the lens is mounted in a brass frame which holds it in position, enabling the dissector to use both hands. A tripod lens will also be found cheap and serviceable.]

2. Do not exterminate or weaken a fern colony by taking more plants than it can spare. In small colonies of rare ferns take a few and leave the rest to grow. It is decidedly ill-bred to rob a locality of its precious plants. Pick your fern leaf down close to the root-stock, including a portion of that also, if it can be spared. Place your fronds between newspaper sheets and lay "dryers" over them (blotting paper or other absorbent paper). Cover with a board or slat frame, and lay on this a weight of several pounds, leaving it for twenty-four hours; if the specimens are not then cured, change the dryers. Mount the prepared specimens on white mounting sheets. The regulation size is 16-1/2 by 11-1/2 inches. The labels are usually 3-3/4 by 1-3/4 inches. A sample will suggest the proper inscription.

HERBARIUM OF JOHN DOE
_Ophioglóssum vulgatum_, L.
(Adder's Tongue)
Willoughby Lake, Vt.
August 19, 1911. Wet meadow.
Coll. X.Y.Z. Rather common
but often overlooked

Place the label at the lower right-hand corner of the sheet, which is now ready to be laid in the genus cover, usually of manila paper 16-1/2 by 12 inches.

It is well to jot down important memoranda at the time of collecting. This is the method in use at the Gray Herbarium in Cambridge. It can, of course, be modified to suit one's own taste or convenience. The young collector can begin by simply pressing his specimens between the leaves of a book, the older and coarser the better; and he can mount them in a blank book designed for the purpose, or if he has only a common blank book, he can cut out some of the leaves, alternately with others left in place, as is often done with a scrap book, that when the book is full it may not be crowded at the back. Or he can use sheets of blank paper of any uniform size and mount the specimens on these with gummed strips, and then group them, placing those of the same genus together. Such an extemporized herbarium, though crude, will serve for a beginning, while stimulating his interest, and advancing his knowledge of the ferns. Let him collect, press, and mount as many varieties as possible, giving the name with date and place of collecting, etc. Such a first attempt may be kept as a reminder of pleasant hours spent in learning the rudiments of a delightful study.

We cannot insist too strongly upon the necessity of handling and studying the living plant. Every student needs to observe for himself the haunts, habits, and structure of real ferns. We would say to the young student, while familiarizing yourself with the English names of the ferns, do not neglect the scientific names, which often hold the key to their meaning. Repeat over and over the name of each genus in soliloquy and in conversation until your mind instantly associates each fern with its family name--"_Adiantum_," "_Polystichum_," "_Asplenium_," and all the rest. Fix them in the memory for a permanent asset. With hard study and growing knowledge will come growing attachment. How our great expert, Mr. Davenport, loved the ferns! He would handle them with gentle touch, fondly stroke their leaves, and devoutly study their structure, as if inspired by the All-wise Interpreter.

"Move along these shades
In gentleness of heart: with gentle hand
Touch--for there is a spirit in the woods."

KEY TO THE GENERA

This key, in illustrating each genus, follows the method of Clute in "Our Ferns in Their Haunts," but substitutes other and larger specimens. Five of these are from Waters' "Ferns" by permission of Henry Holt & Co.

As the indusium, which often determines the name of a fern, is apt in some species to wither early, it is important to secure for study not only a fertile frond, but one in as good condition as possible. For convenience the ferns may be considered in two classes.