W.J. Hodgetts. 
I 1 2 
with the thin basal wall, which, according to Hieronymus, is also 
of cellulose, the peripheral region of the cell being surrounded by a 
thick sheath of gelatinous pectic substance. This gelatinous sheath 
(Gallertscheide) is practically unstained with Congo-red but very 
readily takes up such stains as methylene blue, methyl green, 
safranin and fuchsin, its composition being apparently the same as 
that of the seta. Especially in the older individuals it may be seen 
that this sheath overlaps to a certain extent the edges of the 
cellulose “cap” (cf. Fig. 1, B). The very young plant which arises 
from a zoogonidium, at first possesses a uniformly thin membrane 
which does not take on a distinct colour with either Congo-red or 
chlor-zinc-iodine. In a slightly older individual the convex part of 
the wall, as sometimes also the flat basal part, may be stained with 
Congo-red—less distinctly with chlor-zinc-iodine. About this stage 
a peripheral ring of gelatinous substance is observed, and, according 
to Hieronymus, 1 this is secreted by the protoplast through a circular 
split which makes its appearance in the originally continuous 
cellulose wall, separating the upper dome-shaped portion from the 
flat base. The gelatinous sheath is thus not derived from the 
original cellulose wall hut is directly secreted by the protoplast. 
The process is not very easy to follow owing to the difficulty in 
finding individuals in the right stages of development, the early 
stages being passed through very rapidly. The sheath grows 
considerably in thickness and also in a vertical direction, thus 
pushing the cellulose “cap” further from the base of the cell, the 
edges of the sheath, as already stated, later overlapping the lower 
part of the “ cap.” When stained with safranin or fuchsin the 
gelatinous sheath shows a distinct radiating fibrillar structure such 
as is shown by the sheaths of many Conjugate. 
The bright green chloroplast is single, with the form of an 
inverted watch-glass, and lies against the upper surface of the cell, 
where it is most favourably placed for receiving the light. A single 
conspicuous pyrenoid is usually present in the chloroplast, but the 
larger individuals have frequently 2 or 3 (rarely 4) pyrenoids. 
Hieronymus seems to have mistaken small granules of some other 
nature for pyrenoids, for, speaking of the latter, he says,* “ bei 
mancher Individuen werden dieselben sehr zahlreich sodass man 
bisvveilen 50 und mehr davon zahlen kann 1” He also states that 
there is no amylaceous envelope (Starkehiille) to the pyrenoid ; but 
1 loc. cit., p. 357. 
2 loc. cit., p. 359. 
