Geothallus tub ero sits, Campbell. 505 
part, with the neck of the archegonium, is carried up on the 
apex of the capsule. The basal part remains as a sheath 
surrounding the short seta, while the foot is completely sunk 
in the thallus. 
Formation of the Tubers. 
\ 
The first indication of the formation of the tubers in the 
female plants is evident almost as soon as the first archegonium 
is fertilized ; but in the shoots where no perfect sexual organs 
were developed, and in the male plants, it is of course inde- 
pendent of fertilization. It begins by the accumulation of 
granular matter in a group of interior cells near the growing- 
point, which soon is very evident in section as an opaque area 
of varying size. This area rapidly spreads until it occupies 
the greater part of the axial tissue of the shoot, and its limits 
finally become very sharply defined. Later the chlorophyll 
disappears completely from these cells, and those which 
immediately surround the developing tuber have their walls 
thickened and form the rind. We have seen, however, that 
this rind does not extend over the growing-point itself, whose 
apical cell and the immediately adjacent tissue remain prac- 
tically unchanged, and ready to resume active growth again 
when the conditions are favourable. The leaves and outer 
tissues of the thallus finally die, and in the fruiting plants the 
spores are set free by the decay of the walls of the capsule. 
Germination of the Spores. 
A small number of spores sown in October germinated 
promptly, and some of the earlier stages were seen ; but 
another sowing made later was unsuccessful, so that the account 
here given is necessarily very incomplete. A very long germ- 
tube was formed in all the cases observed (Fig. 39), and into 
this the granular contents, largely in the form of oil-drops, 
pass. Very little chlorophyll is present at first, but this 
rapidly increases in amount. The end of the germ-tube, 
where the granular protoplasm becomes much denser, is cut 
M m 
