92 
Humphrey . — The Development of 
The Antheridium. 
The antheridia occur singly or in groups of two to four along the 
dorsal surface of the stem or near the bases of the leaves. They are 
spherical or somewhat oblong in outline, and are attached by means of 
stalks of variable length, though normally equal to the diameter of the 
antheridium-body. The stalk is composed of four rows of cells, and is 
slightly inclined to the plane of the stem surface of the thallus. Mature 
antheridia first appear as pale yellow or as orange-coloured organs, this 
change of colour being due to the breaking down of the chlorophyll in the 
wall-cells, and, to a certain extent, to the large mass of mature spermato- 
zoids within. The antheridia are devoid of any envelope, thus differing 
from Geothallus or Sphaerocarpus , plants which in many respects resemble 
F. longiseta. In Fossombronia the antheridia mature in some instances 
within three weeks after growth of the thallus is resumed, and they appear 
in increasing numbers until about January i, after which time their normal 
development ceases. Under certain unusual climatic conditions, such as 
have prevailed in California during the past winter and spring, antheridia 
have gone on developing and maturing in considerable numbers throughout 
the entire season. This, however, is to be considered as quite abnormal, 
and may be accounted for by the excessive late rains, and warm winter and 
early spring temperature. 
The antheridia arise from single dorsal cells of the younger dorsal 
segments. In this respect their origin agrees with that of the antheridia as 
described by Campbell 1 for Sphaerocarpus and Riccia , and by Leitgeb 2 for 
F. pusilla. 
Developing as they always do at the base of a leaf which in its early 
growth extends over the antheridium, there is thus afforded a protective 
covering to the young organs beneath. By the time the antheridium is 
nearly mature the leaf has unfurled, leaving the antheridium exposed 
to a normal amount of light and moisture. The initial cell of the anther- 
idium is somewhat larger than the neighbouring vegetative cells, and is 
readily distinguished from them by its deeper staining qualities, no doubt 
accounted for by the somewhat larger nucleus and denser protoplasm. 
Just previous to the first division the initial cell becomes considerably 
elongated, extending a third or more of its total length above the surround- 
ing cells. The first division results from the formation of a horizontal 
wall which cuts off the stalk from the antheridium itself. Unlike what 
occurs in the majority of the Jungermanniaceae, the next division, instead of 
being vertical, is horizontal, thus dividing the antheridium mother-cell into 
two superimposed cells, whereas in Sphaerocarpus 3 and Geothallus 4 another 
horizontal wall is formed, thus producing another cell, the two uppermost 
1 Campbell (’95), Mosses and Ferns, p. 79. 2 loc. cit., Heft 3, p. no. 
3 Campbell (’96), vol. x, p. 497. 4 id. 
