ATHYRIUM. 85 



which have been from time to time looked upon as affording 

 so many distinct kinds, are now almost universally considered 

 as different phases of one species. Viewed in this light, the 

 species is certainly not a very constant one, which fact seems 

 all the more inappropriate, inasmuch as the species itself is 

 that to which the name of Lady Pern is applied. All the 

 various forms are plants with delicate and beautiful fronds 

 of annual duration, varying in size from tufts of a few inches 

 high, to plumy masses of the height of three or four feet. 

 The texture is thin, and almost transparent, on which account 

 the nature of the venation and of the connection of the parts 

 of fructification may be here very well seen and studied. 

 They serve to connect the Aspidium-like and the Asplenium- 

 like groups, differing, however, obviously from the former in 

 having the sori elongate instead of round ; although from the 

 circumstance that in age the sori here become somewhat 

 curved or reniform, thus approaching the rounded form, this 

 very species, the Lady Pern, has, by many writers of dis- 

 crimination, been placed in the old genus Aspidmm. If, 

 however, the fructification is examined while young, imme- 

 diately before or after the indusium has burst, its true cha- 

 racter will readily be seen. We have here an illustration of 

 the inconvenience which arises from the preservation only of 



