5G ENGLISH BOTANY. 



base of the frond, and the lower ones are more distant from each other ; 

 the consequence of this is to give a very long and gradual taper to 

 the base of the lamina. The sori are placed very near the margin of 

 the segments ; they are either distinct or coalesce in a line, but do 

 not cover the whole of the lower surface of the frond, but are always 

 most numerous in the apical half of the frond. 



There seem to be no true varieties of this Fern. In 1872 I brought 

 a plant of it from Glen Cloy, Arran, which was the ordinary form 

 with entire segments; in 1878, it is much more robust than it has 

 ever been, and had the edges of the segments conspicuously crenate 

 and undulated too, so it is now what I suppose Mr. Moore calls 

 crispa. The breadth of the segments also varies a good deal. There 

 are a few monstrosities, but none of them very striking. 



Strangely enough, L. Oreopteris appears to have been sometimes 

 mistaken for L. Thelypteris ; it differs by its thick short caudex, 

 with the fronds of each crown arranged like the feathers of a shuttle- 

 cock, by its short scaly stipes and its frond greatly attenuated at the 

 base, and, when fertile, with the margins of the segments not recurved 

 so as to cover the sori, also by the minute yellow glands, which are 

 sprinkled over the under surface of the frond, and which give it a 

 pleasant scent. 



There is some difficulty in deciding whether this Fern ought 

 to be called Oreopteris or montana. There is no agreement 

 amongst botanists as to the limitation of the genera of Ferns, the 

 characters on which the genera ought to be founded being still 

 an undecided question. Very possibly the microscopical structure 

 may afford more natural characters than any at present employed. 

 The lower the plant is in its organisation, the more permanent 

 are the form and structure of the cells and the tissue into which 

 they are combined. It is now generally admitted that the form 

 and disposition of the leaf-cells of Mosses can be advantageously 

 employed as generic characters, while in Ferns the presence or absence 

 and even the shape of the indusium is admittedly liable to variation, 

 and genera founded on characters taken from it present the most 

 incongruous groups. In consequence of this want of agreement as to 

 generic names it has become a general rule that the specific name 

 shall not be changed, and that the first specific name applied to a Fern 

 shall be retained in whatever genus it is afterwards placed. Seeing, 

 then, that the generic name is unstable, and the specific name un- 

 changing, it has become very general, not only amongst fern-growers, 

 but amongst botanists in this country, to speak of Ferns by the specific 

 names only. We speak of Dryopteris, Filix-mas, Filix-femina, etc., 

 without using generic names at all, except in the few cases where the 

 generic name has proved stable and consists of but a single British 

 species, as Osmunda or Scolopendrium, in which it is usual to use 

 the generic name alone. The same practice arising from the same 

 cause occurs in entomology, where in certain groups of moths but a 



