898 



I. FILICES. 



CystopterU. 



Sporangia exposed by 



turning back the 



indtisiam. 



Ceratopteris. 

 Sporangium (mag.). 



Cystopteris, • 



Sporangium opening 

 43y a sort of accessory 

 ring. 



Tnchovianes. 



Sporangium seen in 



front (mag.). 



AlsophUa auslralis. 



Toung archegoninm (mag.). 



(Bornet.) 



Trichomanes. 



Sporangium seen in 



profile. 



Sthizcea pvsilla. 

 Sporangium (mag.). 



Woodsla. 



Sporangia surrounded by filaments 



representing the indusium. 



AlsophUa austf'alis. 



Adult arch^onium 



(mag.). 



over the whole circumference ; these root-fibres are blackish glabrous or velvety, 

 fragile, eylindric, usually mingled with russet scaly hairs, which are often also found 

 on the aerial stem, on the rachis, and even on the principal nerves of the fronds. 

 The fronds are rolled into a crozier before they expand, in such a way that their tip 

 forms the centre of the crozier, and that their lower surface is outside. The petiole 

 {rachis) is cylindric, compressed, or hexagonal at the base ; the blade, usually covered 

 with a stomatiferous epidermis, is sometimes simple and entire, more frequently 

 pinnatisect, or 2-3-pinnatisect ; pinnules sometimes extremely fine (Trichomanes 

 Pluma), nearly always continuous with the midrib of the secondary pinnsB, some- 

 times caducous {Drynaria), rarely membranous, pellucid and deprived of stomata 

 {Hymenophyllum), The nerves of the fronds are slender and well-defined, some- 

 times simple and springing laterally from the median nerve, sometimes forked 

 and dichotomous, and often, in consequence of this dichotomy, forming a network 

 with more or less regular and hexagonal meshes. In some genera they form 

 transverse and regular arches, or large irregular meshes, whence spring short 

 nerves which terminate in the middle of these cellular spaces. Further, the nerves 

 often anastomose in arches near the median nerve, and give off on the outer side 

 simple or forked or anastomosing and reticulate venules. 



The fronds are sometimes furnished with bulbils {Hemionitisy &c.), or are radi- 

 cant {Asplenium rhizophyllum, Woodwardia, &c.) ; they are often very dissimilar in 

 the same species {Platy cerium), some being sterile, others fructiferous. 



