﻿MR 



SCOTT ON THE TREE FERNS OF BRITISH SIKKIM 



11 



growth is confined to the upper extremity ; so that we have exemplified in them both the 



simultaneous and definite modes of vascular growth 



This will be best explained bj 



-!>' 



.pplemental plate which I have added, showing a vertical section of 

 The youngest or nascent leaves are in this wholly composed of 



eference to the 

 Euterpe olwacea 



cellular tissue ; and it is by no means diflicult to trace the origin and development of 

 those vascular bundles characterized by growth at both extremities. The first indications 

 of these are to be found in the younger leaves in the form of parallel lines of elongated 

 cells continuous with others similarly characterized in the stem, wliich by graduated 

 stages of development pass in the older leaves into the normal vascular bundles. These 

 appeared to me to have their 



/ 



origm on the summit of the stem, on lines correspondino' 

 with the axis of the leaves, whence they grow upwards into the leaf and downwards into 

 the stem. 



These are the analogues of, though differing in structure from, the fi 



woody bundles of the Pern stem 



(^ 



In all the Palm stems which I have examined 



gracilis and Catechu, Etiterpe edulis, Arenga saccliarifi 



Caruot 



urens, 



the course 



JBorassus, Livistona, and Cocos nucifera), I find a further concordance 

 of these bundles in the stem, which, proceeding from the base of the fronds, pass moi_ 

 or less into the central parts of the stem, though by no means at a uniform angle, whence 

 with a slight outward curve they pass down and insinuate themselves in a more or less 



parallel manner amongst the adjoining bundles. In 



of the many sections I have 



made, however, could I find any traces of that regulated curving or spiral turning of 

 the bundles, which is usually represented in diagrams of the Monocotyledonous st°em. 

 Henfrey has remarked in his interesting paper on some points in the structure and growth 

 of Monocotyledons (Ann. & Mag. Nat. Hist. vi. p. 183), " In speaking of crossing, it must 

 always be recollected that this term is used rather loosely, as the upper bundles take very 

 variable courses to get to the outer sides of the lower ones .... so that it is only here and 

 there that a section will exhibit a direct crossing like that usually shown in diagrams." 

 This is, no doubt, quite correct so far as a continuity of the individual bundles' is con- 

 cerned ; but it fails to show why in every section of a palm-stem (at least in all that I 



have made) the fibro-vascular bundles 



passing from the fronds towards the 



such had been the 



centre, but none passing thence to the periphery : manifestly if 



arrangement, gygyj radial section of any length ought to have shown at least portio 



of the bundles on both courses, which they certainly do not *. 



1 



The remarkable and frequently sudden enlargement of tlie caudex of certain palms towards the middle has been 

 frequently remarked by travellers in the tropics. Various illustrations of this have been given by ifartius in his 



allace 



confined to the Arecineae. 



. In the 

 observed. 



our 



specimen 



or less marked manner, and afforded me materials for the following observations. „. .^ „. ^..^.^^ 



here is over 70 feet in height, with a basal girth of caudex of 92 inches, tapering upwards to 63 inches at 5 feet 

 whence it thickens upwards to 68 inches at 8 feet, to 78 inches at 10 feet, thence undiminished to the top. Now 

 looking at such a specimen, it is impossible to offer a hint as to the probable cause for the enlargement. Young 

 specimens, however, as it appears to me, are more suggestive. 



Thus 



Ml 



varying Irom 4 to 8 feet, I observed a few with very 



To illustrate, in one specimen the basal cir- 



c2 



