Geothallus tuberosus , Campbell. 501 
inner cells by transverse divisions give rise to the egg and the 
row of canal-cells. The central cells have larger nuclei and 
denser protoplasm than the peripheral ones. In one case 
(Fig. 29) apparently two. ventral canal-cells had been cut off 
successively, and some older ones showed what seemed to be 
evidences of the same thing. The writer has in a former 
paper called attention to a very similar phenomenon observed 
in Osmunda 1 . What the significance of this is would be 
hard to conjecture. The suggestion made with reference to 
Osmunda , that possibly it was something analogous to the 
polar-body of the animal ovum, seems hardly in accordance 
with the phenomena of fertilization known in plants. 
The neck-canal-cell divides first into two (Fig. 27), and later 
each of these divides once more. The wall of the archegonium 
remains single-layered until after it is fertilized. A cross- 
section of the neck of the archegonium shows six peripheral 
cells, as in Sphaerocarpus and the Marchantiaceae, instead of 
only five, the number in the typical Jungermanniaceae. The 
basal cells undergo divisions in various directions, so that 
the pedicel is not clearly distinguishable in the older arche- 
gonium. The venter of the ripe archegonium is not much 
enlarged, and the elongated egg does not completely fill its 
large cavity (Fig. 31). 
As in Sphaerocarpus , the envelope is formed about the 
archegonium whether it is fertilized or not ; but in Geothallus 
it grows more slowly at first, and at the time the archegonium 
opens it does not reach more than about halfway up the 
neck, the upper part of which projects out of the opening. 
Later, however, it continues to grow until it finally becomes 
very conspicuous (Fig. 23). Its form is decidedly more 
cylindrical than in Sphaerocarpus , and the opening at the 
top larger. As in Sphaerocarpus , the neck of the archegonium 
is more or less bent forward. 
1 ‘ On the Prothallium and Embryo of Osmunda Annals of Botany, April, 
1892. 
