Geothallus tuberosus , Campbell. 503 
mediate stages between those shown in Fig. 35 and Fig. 37 
were wanting, so that the important point of the origin of the 
sporogenous and sterile cells must for the present remain 
undecided. A comparison of the stage shown in Fig. 37 
with the corresponding one in Sphaerocarpus shows some 
marked differences. While the structure of the wall is the 
same, the wide space between the mass of archesporial cells 
and the wall in Sphaerocarpus is absent here, and the sporo- 
genous cells are very much larger and entirely free, instead of 
being united with the sterile cells, from which they also differ 
much more in appearance than is the case in Sphaerocarpus. 
The spore-mother-cells in the specimen figured (Fig. 38, a) 
were free globular cells with a thick membrane which 
appeared quite homogeneous in structure. The centrally- 
placed nucleus was not very large, nor was the amount of 
chromatin especially noticeable. In the microtome-sections 
the cytoplasm showed a reticulate appearance like that 
observed in other similar cells, and due no doubt to the 
dissolving out of the oil or other soluble matter by the 
reagents employed in the process of imbedding. The sterile 
cells (Fig. 38, b) are thin-walled and almost transparent, and 
entirely separated from each other. They contain very little 
granular matter, but the nucleus is distinct. 
No specimens were secured which showed the early stages 
in the division of the spores, and the appearance of the older 
spore-tetrads does not show whether or not there is any 
indication of the division of the cell before the nucleus 
divides. 
The Mature Sporogonium h 
The mature sporogonium is a nearly spherical capsule, about 
1 mm. in diameter, connected by the very short seta, which is 
about four cells thick, with the enlarged bulbous foot which 
penetrates into the thallus, instead of being raised above it as 
1 For figures of the mature sporogonium and spores, see the writer’s paper in 
the Botanical Gazette, January, 1896. 
