116- ON THE ANATOMY OF 
the middle nervure, to which they adhere more forcibly, and 
generally separate with it when force is applied. They ap- 
pear to be flat membranes, composed of variously-shaped 
cells, with interstitial, generally triangular spaces. These 
cells contain a variable number of green globules. ; 
The organisation of the leaves of the emerged species is the 
same, but the number of tubes, each of which has a vascular 
fascicle as in Æ. setaceum, somewhat nearer the upper cutis. 
The lateral tubes in these terminate at various points, a 
few only being prolonged to the summit, will necessarily vary 
-with the breadth of the leaf. Thus in E. Wallichianum, these 
amount to 18 or 20, in E. acanthocephalum, to 6 or 8. In the 
former species, and in some others, each tube is partially subdi- 
vided by an incomplete septum, generally attached to the upper 
cutis, occasionally apparently to neither, and containing a vas- 
cular fascicle. The longitudinal dissepiments form the nervures, 
by their attachment to the cutis. The nervures are always some- 
what depressed ; The arrangement of the vesicles is, with ex- 
ceptions of E. acanthocephalum, and E. glaucescens, less sym- 
metrical than that of Е. setaceum. Iu these too, the vesicles are 
attached to both cutes, but chiefly to the upper, and to the 
transverse septa, and vary much in form. 
The under surface of the leaves of all the species І have 
examined, abounds with stomata, and as these exist also on 
the sheaths and peduncles, I shall defer the account of them 
until the two last named appendages have been noticed. 
Sheaths. These have precisely the same organisation in all ; 
not excepting E. setaceum, the sheath of which has gene- 
rally about 10 tubes. 
The tubes terminate in cul-de-sacs, at a variable distance 
from the ends of the sheaths,. which are membranous. 
The same arrangement of the parenchyma, and the same 
structure of longitudinal and the transverse septa occur. Their 
outer surface which obviously corresponds with the under 
of the leaves, abounds in stomata. The number of tubes 
appears to have some relation with that of the peduncle 
