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



complicated arrangement. The vascular system is destitute of the cambium layers, and 

 apparently simultaneously developed with the apex of tlie stem, inasmuch 

 examination of longitudinal sections) we find it as largely developed towards the apex 



(though naturally less hardened) as in the lower and older parts. Cell-development 

 seems to me confined to the flattened apex, aU further poriphcrical increase being due to 

 cell-expansion, as shown hy the enlarged size of the latter as compared with the former. 



Waving, then, the difference in the anatomy of the bundles and the other structural and 

 morphological characteristics of Fymphajas and Ferns, we have evidently a considerable 



analogy in the growth and development of the main axis, in the apparently simultaneous 

 development of the vascular bundles, with an absence of the cambium layer, and in the 

 origin of the adventitious roots from the base (generally) of the rootstalks of the leaves 

 all characters common to both forms. The affinity of the nymphseaceous stem 

 with the mouocotyledonous has been urged by various authors ; and tliere can be no 

 doubt they have many characters in common ; indeed, if we have regard to stem- 

 structure only, the characters, aberrant though they be, are more strongly mono- than 

 dicotyledonous. Here, however, we must be guided by the embryo, which, as shown 

 by tlie authors of the ' Mora Indica,' p. 235, is truly dicotyledonous. . Slight stress 

 can be laid on Treeul's objection that the cotyledons are retained within the seed, 

 which seems to me but a natural adaptation to the conditions under which germi- 

 nation usually takes place. The slightest reflection on the function of these organs, 



and the fact hat the seeds often germinate under many feet of water, teaches us how. 

 by he survival of the fittest," the ordinary mode of development may have been de 

 parted from by arrestmg the cotyledonary development, economizing L then fLble 



leaf to the surface of the waters. The degradation, so to speak, in the structure of the 

 rntlri J Ja S T T. ^'"^ ''"" ^^^''"^"y ^<=''^-<'' S-^^-tion after 



that^ r • :; irnt lYStirirf -n- ^'"-T'^ ''-'" °" "'^ '-- 



it is of hich interest to i..T ,? . ^ bmlding-up of the woody structure, 



The iatere in th—^^^^^^^ '' ''^'^ ^1^°- -der its reduced action. 



order, and the ImpZuveW^^^ '""if '" ''"' ''^°' ^y^^<"^^*^« P^"-'^ of the 



if. under these ^oltZtZZ^^t^fSn:^'' T "f r'"°"^- ^^^ 



SO many cliaracters in common wifl. V. /""^^^^ ^^^ *^^« retrograded and presented 



conditions in which tree Z^ZItt^:: /"? 71 ? "'' ^^"^^"^^^^ ^~ *^-* '^^ 

 and the most placid enwll t^^ 



-atomical characters, which differ only L de^r^^^^^^^^ f ^^ ': «-- ^^- 



geners and which they have so unchangedly retatedt^^ 1 ^'^ ^""^^'^^ ^^" 



many long geological periods. *^^ ^^''^''^^ nro^....;.. . 



S:euerai progression through 



o 



to 



and the di.erenee of dimension." And.'agli IIS 



emarks, " I believe it would 



