MODE OF GROWTH OF BALLIA CALLITRICHA. 217 
Now, having before described the mode of narrowing upwards of the upper ends of the 
joints and their lateral contour (in “ ordinary ” view), it remains to say further that they 
are from both front aspects narrowed upwards—so as to offer a blunt wedge-shape, 
rounded at tip, if they were viewed laterally—and so as to fit into the deep similarly 
figured noteh of the lower end of the joint immediately above. Тһе boundary at the 
summit is somewhat coneave, adapted to the convex base of the interior of the notch of 
the joint above; but as it is considerably narrower, its concavity does not so readily 
strike the eye, and it might be regarded as straight or nearly so. Thus each joint might 
be said to be, as it were, equitant upon or to sit astride the wedge-shaped top of the 
joint immediately below ; its more or less tapering or narrower subdivisions (one of which 
is seen in either ordinary “ front view " of the frond) giving rise to the at first pardon- 
able enough error, that there is a projection into and introversion of the cell imme- 
diately below. 
Thus the true state of affairs is just the reverse of what one naturally is first inclined 
to imagine; it is the base (not the summit) of each joint which is introverted to make 
room for the tapering upper end of the joint immediately below it. But this introversion 
takes place in the peculiar manner and gives rise to the configuration described—this, as 
it were, ‘ splicing together ” of the joints doubtless adding to the tenacity of this rigid 
alga. That this is the true explanation I have satisfied myself by breaking up a small 
portion of the plant, and as muchas possible denuding little fragments of their branches ; 
and I thereby succeeded in getting a lateral view of a filament, otherwise necessarily, as 
has been mentioned, extremely difficult to obtain. In this view the marginal contour of 
a filament is pretty nearly straight from end to end (Pl. XXVIII. fig. 9). 
From the description already given it will be observed that—owing to the narrowing 
upwards with a curved outline of the upper ends of the joints of the principal stems and 
secondary rachises, and to the peculiar figure presented by the basal end of the joint 
above it, coming down to meet it with the curve appertaining to the inner angle of the 
great “notch” therein—opposite each “splice” there exists what may be called a 
recurring narrowing of the filament (Pl. XXVIII. figs. 3, 14; Pl. XXIX. figs. 13, 17). 
Owing to the peculiar contours of the joints being ignored in the figures extant, as a 
matter of course these shallow sinuses are not represented; the lateral margins are 
shown rather as those of broadly truncato-ovate cells. Still less is there any indication 
that, as is the case, each of these shallow sinuses is filled by a cell (Pl. XXVIII. figs. 
. 18,10, 11, 14; РІ. XXIX. figs. 17, 18). When fully formed, this intervening cell appears 
to be either quinquangular or sexangular, but in different parts of the plant of very 
varying proportional figure. And it is from this cell—never directly from the rachis- 
joint itself —that the lateral branches take origin. 
These lateral cells, which I would denominate *'ramification-cells " are either pen- 
tagonal or hexagonal; and the five or six sides (as the case may be) are of very 
unequal lengths. Two of the sides are apposed to the joints of the rachis; two beyond 
these are external and always unchanged ; and the one or two remaining sides intervene 
between it and a ramiñcation. The longest side in the pentagonal cells is that in appo- 
sition with the whole of the curved (that is, attenuated) upper portion of the joint of the 
