FRUIT OF MELOCANNA BAMBUSOIDES. 413 
break up very readily into their components. The only other contents are a very faint 
plasmatic wall-lining and a very small quantity of oil. The cell-walls are rather thick 
and swell very much in a diluted solution of potassium hydrate. The ordinar y reagents 
for cellulose show that the walls of this par enchyma as well as those of the collenchyma 
are of pure cellulose, with the exception of a thin central lamella. "Towards the inner 
surface of the pericarp the elements of the parenchyma (Pl. 46. fig. 29, p.) decrease 
rapidly in size, being at the same time tangentially slightly flattened, whilst the cell- 
walls exhibit the same character as in the outer parts. The innermost layer which 
borders immediately on the diaphragm, and represents the inner epidermis, is in no way 
differentiated from the small-celled tissue immediately outside it, except in so far as the 
lumina are still more reduced and often irregular, as if the cells had been exposed to 
unequal pressure. This small-celled inner zone as a rule contains starch only in the 
outer layers and in the shape of minute granules; otherwise the principal directly visible 
cell-contents are plasma and some oil. 
The whole of the pericarp is traversed by vascular strands (Pl. 45. fig. 5) which, seen in 
transverse sections, appear arranged more or less concentrically, being most numerous 
towards the periphery. They are directed from the base of the fruit upwards, branching 
here and there but not frequently, and consist chiefly of cambiform tissue and fine 
strands of tracheids. Most of them must have been formed during the growth of the 
fruit, as they are much more numerous than in the ovary. 
The ribs of the fruit, where present, exhibit no special characters in their structure, 
but it is probable that the formation of the collenchyma starts from them. 
B. The Diaphragm. 
In describing the development of the fruit, I pointed out that the diaphragm of 
the mature fruit represents the collapsed and crushed remains of the rudimentary 
endosperm which develops in the earlier stages of the young fruit. Seen in a transverse 
section under a low power it appears as a thin zone distinctly marked off towards the 
embryo, but less so towards the pericarp, from which it differs mainly in its greater 
density, resembling somewhat hardened jelly. Its thickness varies slightly in different 
parts, but without any definite relation to the orientation of the embryo, from 15, to 
50 u or more. It separates readily from the embryo except near the base, but is so 
firmly attached to the pericarp that it cannot be removed, unless it is soaked for some 
time in water, when it swells and may be pulled off in fragments. This lining often 
appears, where it is thinnest, even under a higher power, almost homogeneous (PI. 46. 
fig. 29, d.), with tangential lines of less density and, in places, a delicate tangential striation. 
On the other hand, if we examine it where it is widest, distinct cell-lumina of usually 
tangential extension niay be seen, at least in the part nearest to the pericarp. If these 
sections are, however, left soaking in water or a very dilute solution of hydrate of 
potassium, or in Eau de Javelle, the tissue becomes gradually loosened, and with the aid 
of needles it may be so expanded as to restore GEET the original shape of the 
