26 



forms of Aspidium, American botanists have accepted Hooker's 

 \-ie\vs. Because the sori are long and the indusia are attached by 

 one side to the veins and open on the other side, all of which fea- 

 tures are characteristic of Asplenium, it has been claimed thaty?/T.r- 

 foemina and other species allied with it belong to that genus. But 

 there is another character which essentially modifies this judgment 

 and compels recognition. That is the curvature of the sorus and 

 indusium, by which the upper end of the sorus is curved across the 

 veinlet and back upon itself, often so strongly as to resemble the 

 sorus and indusium of a typical Lastrea, or free-veined form of 

 \ephrodium, distinguished by its kidney-shaped indusium. It was 

 this roundish form which induced Linnaeus to rank it as a I'olypo- 

 dium, and Swartz to place it under Aspidium. These three genera 

 therefore have laid claim to it, with each of which it agrees in a 

 modified degree, but with no one of which it agrees entirely. The 

 genus Athyrium, however, as constituted by Roth, comprises all 

 these features, and completely satisfies all the generic conditions 

 dependent upon its fructification. What those conditions are will 

 best be discovered by taking Roth's own description of the genus, 

 which I have translated from the Latin : 



ATHYRIUM. 



" Capsules distributed in ovate sori underneath the disc of the 

 frond, surrounded with an articulate ring. The involucre springs 

 laterally from the venule, lying loosely in the form of a scale, with 

 laciniate-fimbriate margin, at length elevated inwardly, pressed 

 back and semi-lunar. 



" Observation. The essential character of Polystichum consists 

 in the involucre being either umbilicate or peltate, or reniform, but 

 on every side nearly free. In the first case, at the time of maturity, 

 the involucre is drawn together centrally to its own fixed point, and 

 very often acquires the shape of a funnel ; but in the latter case it is 

 drawn back sublaterally to a fixed point and changes the sub-peltate 

 shape into a reniform shape. 



" But among the Linnaean Polypods there is observed no other 

 of which the involucre has an ovate-oblong shape, and as in Asplen- 

 iniu, springing laterally from the venule, draws itself out following 

 the length of the same. It lies more loosely in a heap before the 

 maturity of the capsule, when from the other side opposite and 

 looking backward it rises a little above the costa of the frond or of 

 the lacinia. Toward maturity, it is raised against the costa by the 



