OF CEYLON AND INDIA. 
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behave like a root-cap, especially like the cap we shall 
presently describe in Podostemon, Hydrobryum, &c. The 
leaves can be seen forming, in large numbers on the upper 
side, and in small on the lower. 
There is no very definite arrangement, so far as I have 
observed, in the meristem, but the peculiar structure of this 
growing point requires further detailed investigation. The 
meristem is small-celled, the cells near the growing point 
being approximately isodiametric, while further back they 
are elongated in the direction of growth of the thallus. 
A desmogen strand of very narrow cells makes its appearance 
in the middle of the thallus at a very little distance from 
the tip. The dermatogen layer is fairly well indicated nearly 
to the very apex. Rhizoid formation begins a little way 
back from the tip, at the region where growth and movement 
are probably completed or nearly so, by the outgrowth of the 
epidermal cells in the usual way. Most of the rhizoids are 
sloped a little forward in many specimens, as if there had 
been a slight growth after they had become affixed to the 
rock. Looking at a growing apex in surface view the 
square shape of the cells near the apex is easily seen, 
and the elongated shape of those further back is very prettily 
indicated by the shape of their contained silica bodies. 
These bodies are abundant in the surface layers of the 
thallus, and have already been described in Tristicha (and 
cf. PL XI., figs. 1, 3). Their presence makes section cutting 
very troublesome. 
To return to the large seedling mentioned (PL IX., fig. 1 2). 
Its growing points are all of the pattern described above, and 
have pretty evidently all sprung from the single original one 
by branching. The branching of the thalli is so near the tip, 
and the two branches are so nearly alike, that it looks like a 
dichotomy ; but though I have not been able to definitely 
decide this point, I think it is really a case of lateral branching. 
The growing point itself is the centre of a cushion of tissue 
thinning off towards the edges. When a branching takes 
place, the two new growing points soon have a sort of valley 
