The Scottish Naturalist. 45 



flexile, and scarcely more than serrate, while the character 

 derived from the veinlets is by no means constant; alpestre hav- 

 ing often unbranched veinlets or only one at the base forked, 

 while flexile has occasionally one of the lateral basal veinlets 

 forked. In habit, however, as Babington points out, and as we 

 will see presently, the two forms are very different. 



Of the characters given by Hooker, none bear close analysis. 

 Of the stipes, he says, that it is short in alpestre, very short in 

 flexile; but, considering the different size of the two forms, flexile 

 has often a stipes quite as long in proportion. In alpestre the 

 pinnae are spreading or ascending, in flexile they are spreading 

 or deflexed — so that in both they may be spreading. All speci- 

 mens of flexile I have seen, however, have deflexed pinnae. 

 Lastly, the pinnules in alpestre are said to be crowded, in 

 flexile rather distant, a character that holds good of neither 

 form. Finally, he says that the pinnae in flexile are short, which 

 seems to be a more constant character, though I do not think 

 that they are really very much shorter in proportion. 



Thus, on examination, one point of distinction after another 

 disappears, leaving only as constant marks the narrow base 

 of the pinnules, the somewhat narrower frond, the whole ap- 

 pearance and habit of the plant. To these I would have added 

 the deflexed pinnae, had Hooker not given them as spreading or 

 deflexed ; and also the fact (mentioned by Babington) that the 

 sori are numerous at the base of the frond, becoming few, and 

 finally disappearing upwards ; but Moore says that this character 

 also is not invariable. I may mention that I have compared 

 the spores of both forms and find no difference. In many ferns, 

 as you are aware, the spores afford good distinctive characters. 



I have said that the general appearance and habit of flexile 

 afford one of the best points of distinction. Alpestre has erect 

 fronds, and its general appearance is, as is well known, very 

 similar to that of Athyrium fllix-fcemina, for which indeed it was 

 long mistaken. Flexile, on the other hand, has somewhat nar- 

 rower and more tapering fronds, with the stipes bent or elbowed 

 a little above its attachment to the rachis, and in consequence 

 the frond is far from erect, and, in fact, in many cases is nearly 

 parallel to the surface of the earth, which, with the deflexed pinnae 

 and the pinnules narrowed at the base, give it a very distinct 

 appearance. In addition, it is almost invariably smaller than 

 alpestre — generally very much smaller — and, though its name 

 implies a more pliant structure than alpestre, I think that in 

 reality it is more rigid. 



