144 



ASPLENIOID FERNS 



[CH. 



and are often strongly recurved, sometimes even horse-shoe-shaped, or more 

 or less reniform, and then they hardly differ (as van Rosenburg remarks) from 

 Lastraea {Dryoptei'is) (Fig. 673). In these features Athyriinn corresponds to 

 some of the less advanced types of Diyoptcris, a fact that concentrates 

 attention upon the details of its sorus. 



The genus Athyriicni was founded by Roth in 1799 {Tent. Fl. Germ. Ill, 58) 

 to receive certain species of the older Linnaean genus Aspleni?ivi, which he 

 found to be characterised not only by hooked or sometimes horse-shoe-formed 



Fig. 67.^. Athyriuin Roth. A, ^ = diagram of transverse section of the petiole o{ A. filix-foemina (L.) 

 Roth, A below, B in upper half. C = A. acrostichoides (Sw.) Diels, primary pinna. D~E = A. Jilix- 

 foeinina. Z' = primary pinna. jS = secondary segment with venation, sori, and indusium. F-H= 

 A. alpesti'e (Hoppe) Nyl. ^=two tertiary segments, with venation and sori. (7, .^=indusium highly 

 magnified. {A, B, F-H, after Luerssen: D, E, after Mettenius: C, after Diels.) From A'atiirl. 

 PJianzeiifatn. 



sori, but also by the structural fact that their receptacle has a special vascular 

 supply. Whereas in Aspleninni the sori are inserted on the vein direct, in 

 Atliyruim a small vascular strand branches off from the back of the fertile 

 vein and i)asses into the receptacle, thus giving it a higher morphological 

 individuality of its own. Mettenius notes this {Farngattungen, VI, p. 57, 

 Frankfurt, 1859), but he does not on that account admit that Athyrium is 

 a linking genus between Aspleninni and Aspidinui. He held rather that 

 Athyrium is at all events nearer to Asplenium than to Aspidium. While his 

 point may be true enough for the classification of 1859, it is to be remembered 



