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



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considerably more elongated and less disposed to ramify and anastomose than are those 

 of A. glabra, so that, as shown in the ahovc-noted plates, their examination is much 

 simplified. Those bundles from the fully matured fronds I have frequently found to 

 have a downward extension of from 12 to 18 inches and upwards, while those from 

 the younger fronds are always much shorter, indicating a certain reciprocity of develop- 

 ment. I am of opinion that the downward development of the bundle is continued until 

 the frond is fully matured. But for such a limitation to the development, the lower 

 parts of the stem would have been much more crowded (and, indeed, ultimately filled) with 

 the descending bundles. This is not the case ; and reflecting on the above relations 

 between the development of the younger and older fronds and tKeir respective vascular 

 bundles, I consider myself justified in holding the above view of the limitation of the 



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growth of the latter. 



As further supporting the view of an inverse or polar development of the free vascular 

 bundles, I would also direct attention to the very marked difference in the ramification 

 of the bundles in the caudex and those in the frond. In the latter they are arranged in 



planes with an almost specific regularity, agreeably to a correlated development 



with the other part ; whereas in the former we find them distributed in a most irregular 

 and complicated manner, which appears to me only explicable when we consider them 

 developed subsequently to the parts in which they are found. Certainly, had they 

 originated at their lowest point (which must have always been in proximity to the 

 growing-point, as shown by their appearance in the nascent fronds); and undergone 

 development with the other parts of the caudex, they must necessarily have extended 

 in nearly straight lines between their points of origin and attachment to the diaphragm 



of the fronds, which, as I have shown, takes place in their earliest sta-es of de- 

 velopment. ° 



Schleiden, in criticising Martius's views on a similar development of the vascular 

 bundles of Palms (Principles of Botany, p. 258), remarks - that he [Martins] has left 

 the meanmg of the term onward growth of a vascular bundle equivocal. If it means 

 that the already existing elongated cells become transformed into vascular bundles, it 

 describes no peculiar process of growth ; the vascular bundles were already to be dis- 

 tmguished m their elementary condition : but if it means that the cells themselves of 

 which the vascular bundles are composed are produced subsequently, originating above 

 first and proceeding downward, this is, I believe, erroneous." If, as Schleiden states, 

 Wul 1 ''T ^""'' ambiguously (though I can scarcely doubt that his 



dMnX 7fZ At r r "^^'""^^ '^^^^ ^* ^^^^ extremities), Gaudichaud 

 tSTle^Z i development commences in the centre, whence an ascending 



"^^^^^^^^ ^"'"^^^ "^^^^^^ ^^''^ ^-^-^h- gen. sur TOrga^o! 



fytenfrt^^^^^^^ ti:i '^ '"''"'"" '' ^"^^ "^^"^' ^^-*-- (-d is supported 



poift of^^^^^^^^^^^ i^ ,r '"" '"'""^'^ ^' *^^ ^^^^^- ^-^- -d-ates the 

 C on tZ W of' 1 ' '"" T"'^ ^^^ '""'^ *^^ ''''' ^-- -y -- observa- 

 We, T t ctrinced thatTr fT f"' ' ^^^^ ^^^ ^^ ^^1^-^-% to examine 

 port on onVortrroth^^ of the above views require modification, and that a 



ly of the woody bundles develops from both extremities, while in the others 



