Page:Encyclopædia Britannica, Ninth Edition, v. 9.djvu/111

 FERNS 101 and the reproductive bodies they bear (spores) germinate without any process of fertilization, and are therefore not to be compared with seeds. The same thing is equally true of the other members of the series Pteridophyta, viz., horse tails, club mosses, selaginellas, &c. A spore on germination produces a structure which, com pared with its immediate parent, is relatively very small, and bears no resemblance to it in form or texture. It is called the prothallium ; it is green and membranous, and attached to the surface of the ground by root hairs in ferns and horse tails ; in adder s tongues and club mosses it is tuberous and subterranean, while in Rkizocarpece and tielaginella it always remains more or less included within the cavity of the parent spore. The function of the pro- thallium is entirely reproductive ; it develops sexual organs of two kinds, archegonia and antheridia, either upon the same or different prothallia. Hence, in contradistinc tion to the sporophore the function of which in this group of plants is purely vegetative the prothallial generation is termed the oophore. History. The older botanists, starting from the study of flowering plants, endeavoured to recognize in all other cases the same characteristic points of structure. They did not doubt therefore, arguing from analogy, that ferns were pro vided with true seeds. Gerarde (1597), remarking the appear ance of young plants of Nephrodiuiti dilatatum in the neigh bourhood of old ones, attributed this to the dissemination of seeds, &quot; for I believe all plants have seeds in themselves to produce their kindes.&quot; No one, however, at this time could say anything definite about the &quot;seeds&quot; of ferns, and they came to be regarded as highly mysterious. It was supposed that they were of an invisible sort, and by a trans ference of properties it came to be believed that the possessor of fern seed would be invisible too. Shakespeare makes Chamberlaine say, &quot;We have the receit of fern-seed, we walke invisible.&quot; Ray ridicules Tragus for spreading linen cloths upon the ground to catch the seed of ferns on the eve of midsummer night, when, as Ray properly observed, it would be indeed astonishing if any fell, seeing that it is not mature till the autumn. Columna in 1648 compared the fern frond to butcher s broom, and identified the fructification in the one case with the flowers in the other. Csesius came to his help, and, having examined the sori of a polypody, &quot; telescopii adjumento,&quot; detected what he supposed to be seeds, but which were probably only the spore cases. W. Cole appears to have been the first to microscopically observe the spores themselves (1669), and Ray himself described the hygro scopic movements of the spore-cases which assist the disper sion of the spores. Morison (1715) seems to have been the first to put the matter to the test of actual experience. He sowed the spores of hart s tongue, and in due course, with out, however, distinguishing clearly the two stages, raised plants from them. This important observation fell com pletely into oblivion, and when in 1789 Dr Lindsay, a Scotch physician settled in Jamaica, responded to a request of Sir Joseph Banks for fern plants from that island by sug gesting that spores would be much more convenient to send, the latter was quite unprepared for the suggestion, which he treated as a great discovery. Dr Lindsay accordingly wrote a paper on the subject (which was published in the Linnean Transaction* a few years afterwards), in which he figured the prothallial stages of Poly podium lycopodioides. The spores of ferns were still, however, regarded as equi valent to seeds, i.e., as the result of a process of fertilization similar to that which precedes the development of seeds in flowering plants. A variety of attempts were made to see in hairs or glands upon the young fronds, &c., something that would do duty for an anther. As late as 1832 Do Candolle maintained the analogy of the prothallium to a cotyledon. In 1844 Nageli discovered the antherozoids, motile bodies which are set free from the antheridium, and which perform in ferns the function of pollen grains. All previous observers had tried to find fertilizing bodies on the vegetative generation, the sporophore, which pro duces only spores. In 1844 the final step was reached when Suminski found upon the prothallia the archegonia, flask- shaped bodies containing a central cell (oosphere) which, when fertilized by the antherozoids, develops into a spore- bearing plant similar to that from which the cycle started. In 1850 Mettenius discovered the details of the reproduc tion in Isoetes. Since that time the researches upon the Pteridophyta have been very numerous, and are to be found quoted in Sachs s Lehrbuch. The whole group of the Pteridophyta may be classified as follows : PTERIDOPHYTA. Cormophyta with, two distinct stages in the life-cycle. Sporophore with high vegetative differentiation. Oophore inconspicuous and destitute of vascular tissue. Class I. Filicincc. Leaves highly developed. Sporangia nume rous on the fertile leaves. Sub-Class 1. Filices. Leaves without stipular appendages. Sporangia epidermal, containing spores of one kind de veloped in each from a single primary mother-cell. Sub-Class 2. Stiimlatcc. Leaves with stipule-like append ages. Sporangia containing spores of one kind developed in each from many endogenous primary mother-cells. Sub-Class 3. lihizocarpece. Spores of two kinds. Class II. Equiset uuc. Leaves rudimentary. Sporangia 5-10 ou the fertile leaves. Class III. Lycopodinm. Leaves small (except Isoctcs}, simple. Sporangia solitary. Sub-Class 1. Lycopodiacccc. Spores of one kind. Sub-Class 2. Lirjulatce. Spores of two kinds. I. FILICIDE. 1. The Filices or ferns proper deserve consideration at greater length, both on account of their numerical preponderance over the other groups, and the popular favour which deservedly attaches to their great beauty and variety of form. Commencing with the vegetative generation or sporophore, the following remarks briefly touch upon the most essential points in their organization. In general habit, although with a certain characteristic ap pearance which, to the experienced eye, is an almost unfail ing distinctive character, ferns are as various in stature and aspect as flowering plants. One genus, Ceratopteris, is remark able for its aquatic habit. The terrestrial forms vary from the Hymenophyllacece, which have the small size and delicate texture of mosses, to the larger forms which attain the size of shrubs, while some belonging to the tropics and the southern hemisphere have a palm-like habit, and are called tree-ferns. Cyathea medullaris reaches 80 feet in New Zealand, and A Isophila australis even greater heights in Australia. The stem creeps on or beneath the surface of the ground as in the common bracken, or climbs up rocks and the trunks of trees (Davallia canariensis). In the latter case it is usually densely coated with im bricated membranous scales. In stems of this typo the internodes or spaces between the insertion of successive leaves (fronds) is consider able, and the growing point is often far in advance of the youngest frond. In a large number of herbaceous ...., ferns, of winch the common male and lady ferns are good examples, the stem is short and erect or slightly inclined (fig. 1). The fronds are developed spirally, and in close contiguity without obvious internodes; they form, viewed from above, in. i.-stem of the Male responding to the detached bases of the leaves with the marks (&amp;lt;&amp;gt; left by the fii&amp;gt;n&amp;gt;- cutar ^ udl &amp;lt;*.
 * S&amp;gt; J&gtfSTmSS.