﻿24 MR, JOHN SCOTT ON THE TREE FERNS OF BRITISH SIKKIM. 



divergence of the fronds gradually passes into the pentastichous; and the until now solitary 

 vascular bundle gives off branches to each frond. These run up the stem in a wavy 



manner, anastomose laterally at the points of origin of the fronds, and form a pcri- 

 pherical network, similar in all respects to the arrangement of the fibro-yascular system 

 in the fasciculate herbaceous species. 



3. The pentastichous arrangement of the frond is in general adhered to until the stem 

 has attained some five or six inches in height and from three fourths to one inch in 

 diameter. By the time the stem attains the above height the vascular system, which 

 previously consisted of slender cylindrical bundles, is now much more developed, forming 

 narrow laminae, and thus reducing much the diameter of the interspersed meshes. The 

 diameter of the stem undergoes a rapid increase ; the angular divergence of the fronds is 

 reduced ; and their five-ranked arrangement gives place to a more complex one. The 

 development of the stem thus proceeds; and on its attaining the height of, from ten 

 inches to one foot, we find that the softer and more ceUular-stemmed species (e. g, 

 A,comosa, A.contaminans) have nearly attained the full diameter of stem, and the fronds 

 their normal arrangement— a condition which is in general attained at a much later sta-e 

 m such species as A. latebrosa, A. glabra, and others characterized 

 development of the fibro-vascular system 



eased 



Longitudinal sections of the stem now present the foUowing appearance ; and for 

 il ustratiye purposes I select A. glubm as presenting the greatest development of the 

 hbro-yascular system, and consequently the most complex conditions. In this species 

 we have a most complicated anastomosing of the woody bundles, which, originating at 



base of he stipes, pass downwards into the interior of the stem, and either curte outward 



e«v IT S' ' •'" "' *; ^"^^'^'""'"^^ ^"""'^ '''^''''' °^ --^- -i* '^-- lower 

 extrem ty free m the inner and cellular parts of the stem. Enclosing these are the 



woody lammce, consisting fct of two blackish-broVn exterior lamina,, fol owed by tw 

 Saturn 'ot si rfr' r^ ''' '''''''^'' P^^'^"°'^^"-' surrounding a eenL 



shatum of soft pale-brown trachenchyma. mixed with thin-sided parenchymatous 

 oritin^'a^ tt troTtV V^'T wf ' bundles proceeds from the centre, or point of 



woody bunrir:;;^:^;, t£ ^^^ tS fit™t.rr " "^ 



extremities ascend The downwn.^ .i, • , '^^ °^ ^^^ ^^^^^ i^ which their upper 



tluis the frond's tce^dlg ^LTaLl tTT.T ' ^ " '''^" '""^ "^^^^^ ' 



8-11 feet, while the descLling' ellr t L ;/;» .T" ' ''"="*'^ "' ^'°"' 



inches, and in one case only hav! I found it aUain 2 fleT ^^^'^^^ "^ ^^^^ &»- 10-18 



6. The other woody bundles of the stipes are riven oiF bv f1,„ i , - 



stem, and form a peripherieal layer in the stinr T, ^ ! ^'"^^^ ^"""^'"-^ °^ ^^' 



Wow the diaphragm of the stipe Is isolated Sis IZr , ", '''' "^'^ ^^™^"'^ 

 bifurcations in the stipes, I have in no instance detected anvt? ""'T'""' '"^''''''''' 

 quent^ occui-s with their lower extremities in the caudex "'' " " ^" 



^ The continued descent of i^ee woody bundles in th; .udices of those species so 



