MODE OF GROWTH ОЕ BALLIA CALLITRICHA AND В. SCOPARIA. 229 
much inflated inwardly towards the cavity of the joint, the median pit at least readily 
enough made out (Pl. XXIX. fig. 5). 
It seems sufficiently surprising the comparatively considerable number of cases in 
which no further development appears to ensue. Sometimes one can trace three or 
four of these ramification-cells in as many joints in immediate succession at various 
parts of a “ tuft” of this alga, and frequently in other places scattered here and there a 
single one. Possibly the rate of growth may be but very slow; and many of those 
incipient ramification-cells apparent іп a given example probably would have gone оп, 
were the plant undisturbed in its native habitat, to the development at some later period 
of further ramifications. 
This process seems to take place simply by the projection of the outer side of the 
ramification-cell in an inflated manner (fig. 5), gradually expanding in an upward direc- 
tion. When about half the length of an ordinary joint is attained, a septum is formed, 
the apex grows onwards, then a fresh septum, and so on, until the definite length of the 
branch is attained; the upper joints finally give off the acuminate spine-like branches, 
and the apical cell becomes itself almost spine-like and acuminate. 
From the peculiar figure, as described, of the ramification-cell the branch has somewhat 
the appearance as if it issued through a lateral cleft of the wall of the joint bearing it; 
and the original inner eonvex boundary of the ramification-cell, being wider than the 
portion issuing from the side of the joint in which it is seated, lends to the whole much 
of the appearance of being a kind of graft, as it were, let in at that side of the joint 
whence it emanates (fig. 8). 
Notwithstanding that the mode of origin of the ramification-cells here seems to 
differ from that in the cortical cells of Mr. Moseley's plant, still, when the branching is 
effected, there is a sufficiently striking similarity in appearance in the “ отай-Нке” 
aspect of the insertion of the ramification, and in the mode in which it stands off from 
the joint bearing it (Pl. XXVIII. fig. 7). 
Towards the lower end of the plant decurrent branches are given off somewhat similar 
to those in the callitricha group; but here they do not seem to form a close “ cortex." 
Their mode of origin seems to be very similar to that of the ordinary branches; but I 
was unable to alight on an example i in as early a condition; primarily the ramification- 
cell seems to be similar. : 
The ramification-cell here, however, when the decurrent branch is formed, does not 
seem to offer as much of the appearance of a “ graft" let in at the side as does that of 
an ordinary branch (Pl. XXIX. figs. 10, 11). When it is fully formed it appears of a 
broadly ovate figure truncated below—that is, cut off there by the septum, dividing from 
it the next joint of the dependent branch; its inner lateral margin projects in a convex 
manner towards the cavity of the joint whence it emanates; and its outer boundary 
projects in a convex manner towards the surrounding medium. But this cellis always 
Subdivided by a septum (2, in figs. 10, 11) into two unequal portions, the origin or 
Significance of which I have been unable to make out. This septum runs in a curved 
manner, its convex side inwards, from about the upper apex (the whole plant being viewed 
vertically) of this truncato-ovate cell to near the outer lower angle (formed by the outer 
SECOND SERIES.— BOTANY, VOL. I. Әк 
