49i 
Geothallus tuber osus , Campbell. 
The ripe tuber in Geothallus is an oval, more or less 
flattened body, consisting of a mass of parenchyma densely 
filled with opaque granular contents, containing much fatty 
oil, but little starch. This mass of cells is surrounded by 
a layer of firm black cells, outside of which is a loose mass of 
dried-up parenchymatous tissue. A section of the ripe tuber 
(Fig. i) shows at once that the bulk of it is derived from the 
central part of the thallus, and that the dark-coloured cells 
composing the inner rind are interrupted in front, where the 
growing-point of the thallus persists unchanged. The loose 
outer investment of the tuber is simply the remains of the 
leaves and the outer tissues of the thallus. 
The anterior end of the tuber is free, and a longitudinal 
section shows that the apical cell of the shoot is still recogniz- 
able (Fig. 3, x). The regular segmentation is perfectly 
obvious, and is in no way different from that of the actively 
growing thallus. The apical cell and the younger segments 
cut off from it do not contain so much of the granular matter 
which renders the other cells of the tuber so opaque. The 
nuclei of the cells are of moderate size, but perfectly distinct 
and readily seen. The mass of cells making up the tuber is 
sharply marked from the outer tissues of the thallus by one 
or two layers of cells with thick black walls (Figs, i, 2), and 
the growing-point is protected by the overlapping marginal 
lamellae or leaves with which the plant is provided. The full- 
grown tuber is from 1 to 2 mm. in length, and about half 
as wide. 
The first experiments in germinating the tubers were made 
in September, and others were made at intervals during the 
autumn and winter. The tubers were taken from the earth, 
and after removing most of the dead tissue about them, were 
placed in a glass vessel with just enough water to cover them. 
The first lot of tubers was put in water on September 21, and 
on October 3 the green shoot was first seen. A second lot 
was placed in water on October 4, and on the 9th the young 
green shoots were already plainly visible. The best results 
and most vigorous plants were obtained from the germinations 
L 1 2 
