A NEW FORM OF CYSTOPTERIS. 



By Willard N. Clute. 



IT is remarkable that some species of ferns produce varieties and 

 forms with fairly constant characteristics, while other species, 

 though quite as variable, never produce plants sufficiently dis- 

 tinct in appearance to be regarded as worth naming. The little 

 Cyslopteris fragilis barely escapes being placed in the latter 



class. It has produced 

 some few variations that 

 have been considered 

 * i?J&J*h<lfi^_^ worthy of name, but 

 ^jj^Sg^f^ none that will compare 

 ^ in individual characters 



with such forms as Pol- 

 ystichum acrostichoides 

 Fig- *■ f. incisiim or Nephro- 



dium crista turn Clintoniannm. It was therefore with consider- 

 able interest that I examined certain specimens collected last 

 year along a rocky wall where the Susquehanna river makes a 

 "great bend" from the north into the State of Pennsylvania. 

 These plants scarcely differ from other forms of Cystopteris fra- 

 gilis in the cutting of the fronds, but the sori present a most re- 

 markable difference. They are more than twice the size of the 

 sori in ordinary specimens and so thickly crowded together that 

 very little of the under surface of the frond can be seen. All col- 

 lectors will recall the small size and 

 evanescent nature of the sori in this spec- 

 ies. The indusium soon withers and the 

 sorus, which frequently consists of only 

 a few spore-cases, is early dispersed or 

 broken up. In the new form, on the con- 

 Fig. 2. 



trary, the sori in addition to being unus- 

 ually large retain their hemispherical form long after the spores 

 are ripened, and are so compact and distinct that if any fern 

 collector was offered a single sorus to identify, he would be 

 likely to pronounce it that of Polypodium vulgar e, at once. 



Considering the important part played by the sori in the de- 

 termination of species, some students might think me warranted 

 in describing this as a sub-species at least. It is as well entitled 

 to such distinction as many recently described, but from investi- 



