184 Mr. A. Henfrey on some Points in the Structure 
between the two latter is the fistular condition of the stem in 
the Grass*. 
I next directed my attention to the lower extremities of the 
fibro-vascular bundles, endeavouring to discover their relations 
with the fibro-vascular system of the roots. Here we meet with 
several modifications of arrangement. 
In the stems I have examined the lower ends of the fibres ap- 
pear to branch and to anastomose with their fellows, sometimes 
forming a distinct fibrous layer. In order to explain the rela- 
tions of these extremities, 1 must point out some peculiarities in 
the cellular system. 
Von Mold has deseribed in the stems of Palms a central region, 
a fibrous layer, and a cortical region. The analogues of these 
appear to me to be present in most monocotyledon ous stems. 
The tissue of the central region is generally composed of spheri- 
cal cells which contain abundance of starch at certain periods ; 
this region, in whieh lie the fibro-vascular bundles, undoubtedly 
represents the pith and medullary rays of Dicotyledons. The 
cells of the cortical region are usually very irregular in form, and 
have large intercellular spaces ; they contain little or no starch. 
In bulbs the central region is inclosed by rather a thin layer 
of the cortieal parenchyma, which is continuous with the bases of 
the coats or scales ; the line of junction of the two regions is in- 
dicated in the very youngest state of the bulb by a darker colour 
and greater density of the tissue. At this line the fibro-vascular 
bundles terminate below, and their extremities, by branching 
and anastomosing, frequently produce a dense layer, the fibrous 
layer of Yon Mohl. The cortical region cannot be made out in 
the culms of the Grasses, and it is not continued distinctly into 
the fiowering-stems of bulbs. In Sparganium ramosum it is very 
much developed, both in the nodes and internodes ; in the former 
it exhibits fibres crossing transversely, and thus weaving, as it 
were, the whole into a dense fibrous coat separating the central 
from the cortieal region. 
The most important point relating to the fibrous layer is, that 
it gives origin to the roots, for there is no direct communication 
between the fibro-vascular bundles of the stems and those of 
the roots. The bundle which lies in the midst of the root of 
Sparganium, and indeed of all the annual roots I have examined, 
is composed of a number of vessels arising in a circle from the 
* An illustration of this analogy between the nodes of the stem of a 
Grass and bnlbs, physiologically denoting a certain degree of independence, 
seems to mo to be offered by the possibility of grafting grasses upon one 
another at the nodes. This has been effected by an Italian botanist, Calde- 
rini, in the Millet, and he also successfully grafted Rice upon Panicnm 
Crus-galli , — See Ann, dcs Sc. Nat. Sept. 18t6. 
