﻿22 MR. JOHN SCOTT ON THE TREE FERNS OF BRITISH SIKKIM. 



Circinaiion, though not peculiar to ferns, is certainly one of their most strikin" 



characteristics. The adaptation of the circinate mode of yernation to the development 



of the young fronds is very evident when we reflect on their early isolated position on 

 the ajds and their acrogenous development — unlike what occurs in Palms and Cycads, 

 both of which are characterized by a straight vernation, though singularly enough wc 



find in all class-hooks the latter order as " frequently represented hy a circinate verna- 

 tion." This occurs in no Cycad which I have had an opportunity of seeing ; certainly 

 not in the genus Cycas, which, if I mistake not, is the one referred to by authors. 

 In all the Indian species of this genus I have found a simply involute vernation, 

 the edges only of the pinnte roUed inwards, and in no case have I observed the 

 rachis rolled spirally downward. This, as in palms, is always straight ; the fronds, 

 an-anged in large clusters, form a mutual protection to the young unfolding parts 

 rendering a circiAate vernation superfluous and, indeed, impossible. In ferns, as I have 

 said, the arrangement of the parts is altogether different. In these we have a flatly 

 paraboloidal terminal apex, on which the young fronds are almost horizontally arranged. 

 The increase of the number of ceUs is entirely confined to very short apical radii, beyond 

 which all increase IS by a simple cellular expansion ; this goes on rapidly, so that the 

 horizontally placed fronds and other parts are, as Hofmeister expresses it, " lifted up by 



fronds and consequently mcreases their liability to injury, which, however r 



a? Tver? f a't™! '' f K'- ^"^ '^'^ '^^'^"- ^^^^ '>'^^"' ^ ^^ tolJZU 



LelSenttf ! u 7 ^ '"r""' "'''''*"'^- ^« '^^^ ^-t ^ -ntrifuga 



development of oeUs passmg mto a similar expansion ; this (i e. the development of the 



^xis) Wasmg outwards, we might theoretically assume that the lonSra L/el p 



apparent even in the rudimentaxy sta! Se fro.lf ? f"' '"r'*^"* '"^""*"^« ^^ 

 meut proceeds so do the differences Tt?. ^ , "'""'■ ^' *^"= frond-develop- 



marked, in the first instat^Ty Tm "e liW^ "' *'^ ^"° ^^' ^-°- -- 



cellular extension, thus givin/thel™7 . ""'"'^'''' """^ ^"^^'^^ hj .unple 



from all chances'of injS ^ ^fttnT^t ZTT °'^*'"^' ^"' """'' ^'^-^^ 



a comparatively rare mode of vernation .h.Z T °"™''' *''=»* circination, 



(Broseracc»>), and further, af I Z XlS^'^?! ''^'''-''^ '=h='-'=terize Sun-dews, 

 economy of these plants-^n opinTn wS hi tv f ""l! f^^^ ^^^^ ««-« Purpose in the 



ou the manv inlk „,.,-„i,T° ^^'?'' ^ ^"^'^^ ^'1^ be 'readily admitted on r«fl.nH.„ 



IS 



renderin 



many insects wHch haunt and 



reflecting 



^dering very necessary some such protectiv ' ?°° *'"^ "^^'^^^^^ ^^^^-V 



that afforded by a eirlatc mode of veil: T^ I '''• '''''"'''' "^^-^^pi - 

 — of the Boragine* and others has n 2' "°'*'°" '" '^' inflorescence, as in 



ers, has, I believe, more relation to the fertiUzation of 



