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MODE OF GROWTH OF BALLIA CALLITRICHA. 225 
the branch or lateral rachis are more deeply overlapped (in the manner described) than 
are the upper cells. Ав one proceeds upwards the overlapping is seen to be less and less 
pronounced; that is, the curve downwards in front of the subdivision of the bases of 
the component cells of the branch becomes less and less arched ; whilst near to or at the 
top they appear hardly at all to overlap. 
The cells very gradually diminish in size upwards ; in other words, the branches gra- 
dually taper. Тһе increase in length of the branch is effected only by the growth and sub- 
division of the terminal cell, the next lower cell never subdividing again (unless, of course, 
it should produce ramification-cells). During the progress of the growth of the branch 
the terminal cell appears to be rounded at the top ; but when the branch attains its full 
length, and apical growth is over, the terminal cell becomes drawn out, long and conical, 
its summit acuminate, and its membrane thickened. 
Imay add that the cell-membrane, especially of the principal stems or ramifications, 
appears to be irregularly and longitudinally distinetly, though faintly, striate. 
With the exception of the **stipule-like" secondary branchlet (given off from the 
ramification-cell of the second degree), the ршиз (in Mr. Moseley’s plant), in com- 
parison with other forms, very seldom ramify ; that is, they give off pinnules only here 
and there very fitfully. However, this lower external branchlet, unlike an ordinary 
pinna or pinnule, as has been seen, is not an ultimate emanation from the same series 
of cells (or, in other words, from the same subsidiary ramification) as the pinnæ proper, 
but it is a collateral and ultimate emanation from a series of cells (forming a main stem 
or а ramification) of a generation back. This collateral or accessory ramification, then, is 
as much an independent branch as the older one above, although it might (in error) be 
taken for a pinna springing therefrom. But inasmuch as this accessory branch is but a 
subsequent emanation, primarily owing its origin to the ramification-cell of the second 
degree, which in turn was formed by the subdivision of the primary ramification-cell, it 
could not therefore exist without having been preceded in time by the (larger) branch 
immediately over it, at the outside base of which it stands. : 
The secondary or subsequent rachises in Mr. Moseley's plant, and their simple 
branches or pinnze, are usually pretty stout, taper very slowly, and stand off from one 
another at an acute angle, here and there often in a very scattered and irregular manner, 
giving off solitary branchlets, or little groups of pinnules—it need not be said, each ever 
preceded by a ramification-cell. It will be seen, then, that we have a plant of a соп- 
siderably long-drawn-out and fastigiate habit. Though the branches and pinne lie pretty 
much in a common plane throughout, still the plane may be more or less altered 
through the extent of the aggregate formed by a plant of, say, a few inches in length 
(PL XXVIII. fig. 2). 
It would be a very diffieult matter, perhaps hardly possible, to trace out correctly the 
different layers or laminze of the very thick walls of the rachises up into their rami- 
fications. It seems that an outer layer of possibly numerous thin laminz, forming a 
portion (the upper) of the original wall of each joint of a stem or rachis, reaching from 
ow upwards, becomes diverted laterally, and thus continued forms the outer layer of 
the lower exterior wall of the ramification-cell. But soon afterwards, owing to the 
