POLYPODIUM. 81 



nately branch the veins which ramify in the lobes ; these 

 veins, in average specimens, are pinnately branched, with 

 a simple venule directed towards each marginal tooth. 

 The sori are sometimes produced only on the lowest 

 anterior venule of each lobe, and they then form a series 

 on each side the midvein ; but sometimes more of the 

 venules are fertile, and the sori then range in short lines 

 near the margin of the lobes. 



The very distinct and constant variety called flexile, the 

 Pseudathyrium flexile of Newman, has so peculiar an 

 aspect, that it is scarcely to be wondered it was thought 

 a distinct species. It differs in -its lax spreading habit, 

 narrow gracely- curving fronds, and short deflexed pinnae, 

 with fewer and smaller pinnules. The cultivated plants, 

 which are very constant in character, generally produce 

 almost stalklcss fronds, and these often bear their sori 

 abundantly at the base, but scarcely, if at all, on the upper 

 parts. These latter marks — the almost sessile fronds, and 

 the usually basal sori — disappear in some instances, both 

 in the wild and cultivated specimens. An imperfect indu- 

 sium has been observed, on some of the sori, in the plant 

 under culture, but this occurs only on the least perfect 

 Bori, and appears to be rather an abnormal development of 



G 



