The appearance of these archegones is contemporaneous with that of the fertilising apparatus which makes its appearance in the centre of the terminal rosette of the different urn-bearing stems. The Polytrichum are, then dieceous. These supposed fertilising organs consist of small greyish elongated bodies (as represented in 4, Fig. 891). They are more or less spindle-shaped, and they are accompanied by cylindrical fillets, called paraphyses, or cellulose sacs, which open from above, leaving their contents to escape by abrupt jerks at given moments until the organ is completely emptied.

When the matter thus ejected is carefully examined, it is found to consist of a tissue very distinctly resembling rings of mail, in which each cell encloses a small body rolled up into a ball, with a very perceptible swelling upon one point of its circumference. These little bodies are in a continual state of rotatory motion; the tissue which contains them dissolves quickly on contact with water. The little sac, which is called the azntheridium, becomes flat and dry after the emission of the movable corpuscles which it contains. These are antherozoids. We have said that the appearance of the archegonium is contemporaneous with the antherids. Whatever difficulties may appear to oppose themselves to the idea that these antherozoids become archegones, it is impossible to deny that such transposition takes Place, for on the archegones of certain mosses living antherozoids have been found which had already traversed one-third of the length of the neck. It follows, therefore, from the structure of the archegonium and antherids, and from the curious observations which have been recorded, that there is now little doubt of the sexuality of these little plants. This is further confirmed by the fact on which edwig founds his principal argument, namely, that in the dis- “cous mosses the archegones arrive at maturity when individuals shed with antherids grow in the same neighbourhood.

Fimices, or FErns. In their most graceful type—the Tree Ferns—this order of Ns rivals the most beautiful Palms. When they have | Tr 2 web ie

attained a height of forty or fifty feet their stems form a noble column, some five or six inches thick, from the summit of which flows a panicle of pinnate leaves intersected by a thousand incisions, the terminal tuft which crowns the summit of the trunk curving at all times into a sort of cross, whose graceful curve adds greatly to the elegance of the tree. Their chief anatomical peculiarities are as follows:— The leaves are termed Fronds, and they bear the organs of fructification in little cups or receptacles on the edges, or on the under surface, in the form of little masses of granules, termed sori, consisting of a containing organ termed sporangia, theca, or capsules, surrounded by a ring termed gyrus, or annulus, and a number of contained cells termed spores, or sporules, from which the new plant is produced. The foot-stalk of the leaf or frond is called a stipe, and. consists of bundles of bare woody fibre and scalariform vessels, connected together by cellular tissue, which pass down into the stem under the bark, forming the zones of the wood. In the Tree Fern the rind or bark consists of one or two layers'of

_ Fig. 337.—Stem and section of a Tree Fern. cellular tissue, and is marked from top to bottom by the cicatrices left by the fallen leaves (Fig. 337, a). These cicatrices occur irregularly and at considerable distances apart near the foot of the tree, but at regular distances and almost close together towards cap summit of the stem, showing that its leaves are produced at the top and in successive clusters, and that the trunk has inereased ™ height after the fall of the leaf. Again, a large portion of the transverse section of the trunk is seen to consist of cellular tiss¥°? -

Plate II.—The Arborescent Fern of Brazil.

and through this the wood passes, the centre being occupied by a mass of scalariform duct, so called from the resemblance which ‘its perpendicular sides and transverse lines bear to the sides and rounds of a ladder. This form of tissue is interrupted by large spiral vessels; the wood is also arranged in circles, or bundles, with a wavy outline, but only near to the bark. These circles seem to be sent down from the fronds, and as the fronds surround the stem, the bundles sent down from them lie side by side until they form a cirele. There is a peculiarity in the growth of the Tree Fern, that the interval between the cicatrices enlarges as the tree increases, showing that the stem of the tree increases in height not only at the apex for the time being, but afterwards in the body of the - trunk. The mode of germination in the Ferns seems to be this:— The sporule, after extrusion from the sporangia, bursts its envelope and emits a leafy expansion from its centre, which 3 subsequently forms a bud and 2g then a plant. Plate II. repre- “abi: sents the Arborescent Fern of es och the Brazilian forests. Th aE In our climate these Acrogens cone are far from presenting the ee “ dimensions which they attain APRA ‘ m the tropics. Our Ferns are [ only perennials, with a short rhizome or spreading roots, Whose leaves rarely exceed four or five inches. Even in the tro- Pies and in the southern hemis- Phere the Lymenophylleum 7. and Trickhomanes (Fig. 338), Which grow only in humid aa Places, at the foot of old trees, or upon rocks bathed in running Tooks, are generally of small size. The delicate leaves are desti-

tute of epidermis, and consist of a simple blade of cellular tissue

Fig. 339.—Male Fern.

Fig. 340.—Lower surface of the Frond.

Fig. 341.—Magnified portion of the lower surface.

traversed by nervures formed themselves of scalariform vessels.

In order to study more closely the structure of a fern, let us examine the Nephrodium filix-mas., commonly known as the male fern (Fig. 339). This plant is common in the woods and sterile places. It carries upon its subterranean stem, which creeps along horizontally, certain reddish scales. The leaves are large, petiolate, and much intersected. On the under surface of the leaves, or of what has the appearance of leaves, and which, as already stated, are called in the language of botany, fronds, we find little rounded, or, rather, kidney-shaped projections. Each of these projections are formed by groups of small bodies, yellowish green at an early age, brown

Fig. pias ona of of the ig. ——

at their maturity, and which are covered by a thin greyish sporanges bears pellicle. Each group of these little bodies or the name of sori; the pellicle which covers them is called the representation of the magnified Fig. 341 is a greatly indusium. — which occur on the lower surface of the fronds of the male : ern. cellulose pedicellate (Fig. 842) are or capsules The sporanges entire circle almost with an circumference on their sacs, furnished than the other parts of the wall. and thicker of cellules, larger or by certain growth, These cellules form a sort of ring, which by rupture the irregular determine seem to changes, hygrometric movements: (Fig. 343), and by these capsule of the walls of the Pour out a number of egg-like irregular globules, which were to be the seeds of the plant, and were called considered ‘pores. But this assimilation is ascertained to be absolutely 2

opposed to the facts. In the diverse genera which constitute the great family of Ferns, the apparatus under consideration has very different functions. In the Polypodacee the rounded sori are destitute of indusium. In Pteris it extends along the edge of the frond, and opening from the inner side, protects the sori. In Scolopendrium, the = approaching by pairs, are protected by an indusium, which 1s 0 all appearance bivalve, and disposed in oblique lines. In Osmunda the capsules form terminal clusters upon the nervures of the upper parts of the frond, contracted and modified, and often destitute of the ring as an indusium.

The reproduction of ferns has been closely studied in our days by Herr Negeli, a distinguished German phytologist, and still We shall follow the more recently by Herr Leszcyc-Suminski. ‘curious observations of botanists in their revelations of the strang® mode of reproduction among the ferns, remarking, however, that the investigations of Mr. Henfrey and other observers, Eng and foreign, of high reputation, while confirming many. Herr Suminski’s observations, draw other inferences from them, M. Thuret, a highly judicious guide, preferring to suppose wie the true fructification of these plants still remains to be a covered, It had long been known that the so-called spores of ferns were susceptible, in favourable conditions, of germinating and repr _ ducing the original plant, and this is the generally received ee of its development: the capsules or sporanges are consi “a be the female organs; and the male organs are supposed aes found in the hair-like glandular filaments found in their vieinity- Some new and remarkable observations, however, have shown that the phenomenon was not so simple as it was thought. ” structure of the body which was supposed to be the male anger did not correspond with the antherids of other ¢ | Neither had the presence of antherozoids confirmed the eet assigned to them. In short, nature has neither placed the antherids of the ferns in the middle of the sorus, nor upon the pedicels of the capsules. Contrary to the provisions d a5 by theory, it is upon plants in procees of germination that we sit these organs; upon individuals which have only been in existen®®

for a few weeks, and which still consist of only a small number of cells. For this most important discovery we are indebted, in the first place, to Herr Negeli, and it was confirmed some year later by the observations of Herr Leszcyce-Suminski. eee

If we follow the germination of a fern-spore with Herr Suminski, we find that its external membrane, resistant and coloured, is broken, and by the opening thus formed in the external membrane issues, in the form of a sort of tube, certain cellules reproducing and multiplying themselves at the extremity of the tube. From this there results sometimes a small foliaceous expansion, heart-shaped, in the form of a pear (Fig. 344, a), whose dimensions in Pteris serulata may be an eighth « @* of an inch bya tenth. In —_ the upper part of this small organ or prothallium would appear in due course the root or radicle, then the antherid, and finally the archegonium would appear.

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