422 SYSTEMATIC BOTANY. 



Hymenophyllece the sporanges are attached to little columns formed by 

 the production of the ribs beyond the margins of the leaves (y, /*), be- 

 coming at the same time enclosed in cup-like receptacles formed from 

 the margins of the leaf. In the Ophioglosseae a portion of the leaf is 

 transformed into a simple or compound spike- like process, covered with 

 free spore-cases destitute of a ring, and splitting regularly to discharge 

 the spores (o). 



The spores are simple cells of microscopic dimensions, furnished, like 

 pollen-grains, with a double coat, the outer of which is generally similarly 

 marked' with papillae, reticulations (/?), &c. 



The term " flowering " fern is erroneously applied to those kinds in 

 which the fertile leaves or lobes are destitute of parenchyma, and thus 

 resemble superficially the spadices of Phanerogamia, as Osmunda, Botry- 

 chium, Ophioglossum, &c. 



The arborescent Ferns belong to the Polypodiese and Cyathese, and 

 differ only in habit and dimensions from the more familar forms. 



Ferns are sometimes reproduced by buds, analogous to bulbils, formed 

 on different parts of their structure, and sometimes at the points of the 

 leaves. 



The spores of the Filices retain their germinating power longer, as a 

 rule, than those of the Equisetacese. They have usually a granulated ap- 

 pearance, with a cuticularized exospore. On germinating, the exospore 

 bursts, and the contents, already divided into several cells, are protruded, 

 and from it arises the prothallium. The prothallia of Ferns differ from 

 those of the Equisetaceae in being generally more regular in outline. They 

 produce numerous root-hairs and are self-supporting. The antheridia and 

 archegonia naturally differ, though but slightly, from those of the Equise- 

 taceae in form, but a^ree with them entirely in the details of function. 

 The antheridia are situated on the margin or surface, and the archegonia 

 on the surface of the prothallia. They are monoscious, but show in some 

 cases a tendency to be dioecious. After the embryonic cell of the arche- 

 goniuni has been fertilized by a spermatozoid, "the asexual generation 

 arises from it in a similar manner to that described as occurring in the 

 Equisetacese. An exception to this is to be found in the property of certain 

 prothallia of propagating the asexual generation in a purely vegetative 

 manner. The prothallia of Pteris cretica were found by Mr. Farlow to do 

 so without ever having been seen to produce archegonia. 



Affinities, &c. The Filices constitute a very large and natural group of 

 Cryptogarnous plants which have no very close relations, as regards 

 general structure ; but the Ophioglossece seem to form a link between 

 Osmundea and Lycopodiaceae. As regards the physiological processes 

 occurring in reproduction, this Order must be classed with the Equise- 

 taceae. There is, however, great diversity of habit in the vegetative body, 

 which, as a whole, may be expressed by saying that the leaf predominates 

 in the Ferns and the stems in the Horsetails. 



The Ophioglosseae depart importantly from the general characters, both in 

 their foliage and their reproductive organs ; to the form of the latter there 

 is an approach in Marattieae, and perhaps we may admit that the sporanges 

 of this Order are really like those of Lycopodiaceae ; the development of 

 the young spores appears to agree, however, with that of the Ferns and 

 Equisetacese, which is on a totally different plan from that of Lycopodie<ie. 



