504 Campbell . — The Development of 
in Sphaerocarpus. This is due to the more nearly sessile 
position of the archegonium in Geothallus. The wall of the 
capsule is composed of a single layer of large almost black 
cells, which before it ripens are filled with starch which mostly 
disappears later. The foot is globular or sometimes oval in 
outline, and its cells much distended and containing abundant 
protoplasm and large nuclei, showing that they are actively 
engaged in the nutrition of the sporogonium. 
The spores are very large, and at maturity separate com- 
pletely. They are nearly globular and range from 1 20-140 /x 
in diameter. The wall is very thick, and in section shows two 
well-marked layers, the perinium and the exospore. An 
endospore of cellulose is probably present, but in microtome- 
sections is not clearly differentiated from the inner layers of 
the exospore. The perinium is almost black and appears 
perfectly homogeneous : it is quite smooth except upon the 
ventral surface of the spore, where it is folded so as to produce 
reticulate ridges which in section have the appearance of 
spines. These foldings extend to the inner spore-coats as 
well. No chlorophyll is present in the ripe spore, but no 
further study of the spore-contents was made beyond noting 
that the nucleus is small, as is usually the case in Liver- 
worts. 
The sterile cells, which doubtless are the homologues of the 
elaters of the more specialized of the Hepaticae, reach a length 
of 48-108 /x, being relatively longer than the corresponding 
cells of Sphaerocarpus. They contain some chlorophyll and 
a few scattered granules apparently of albuminous nature, 
but little or no starch was detected in any of the specimens 
examined. 
The sporogonium does not break through the calyptra 
until a much later period than in Sphaerocarpus , and traces of 
the calyptra remain until the sporogonium is almost ripe. 
The first divisions in the cells of the venter coincide pretty 
closely with the first wall in the embryo. Except at the base 
it remains two cells thick for the most part. Finally it is 
torn asunder by the expanding sporogium, and the upper 
