496 Campbell . — The Development of 
genera of Liverworts. Some of the specimens examined 
strongly recalled F. longiseta , a common and characteristic 
Californian species. From P etalophyllum , with which Geo- 
thallus seems to agree in the general form of the thallus and 
arrangement of the leaves, it differs essentially in the absence 
of anything resembling the anterior leafless prolongation of 
the thallus described and figured by Leitgeb 1 . Unfortunately 
this genus does not occur in the United States, so there was 
no opportunity of examining the plants themselves for 
purpose of comparison. 
Under favourable conditions the sexual organs were mature 
within a month from the time the dry tubers were placed in 
water. Those started in the spring and the first ones started 
in the autumn did not produce normal reproductive organs, 
although these began to form. Most of those started after 
January i also failed to mature the sexual organs, and in 
some of the plants grown from these belated plantings the 
reproductive organs were almost entirely wanting. Geothallus 
is dioecious, but there is not much difference in the size and 
general appearance of the male and female plants, in which 
respect it offers a strong contrast to Sphaerocarpus , where the 
male plants are very much smaller than the female. 
In their position and general structure the sexual organs 
resemble those of Sphaerocarpus , and each archegonium or 
antheridium is surrounded by a separate envelope, that about 
the archegonium becoming very conspicuous. As a rule the 
sexual organs are produced less abundantly than in Sphaero- 
carpus, but are decidedly larger. The time of their first 
appearance varies a great deal, in some cases being evident 
when the young shoot was not more than a millimeter in 
length ; but in most cases the young thallus had reached 
a length of several millimeters before the youngest ones were 
to be detected. Where the development of the sexual organs 
was partly suppressed, the envelope was not usually fully 
developed, and projected but slightly above the surface of the 
thallus, recalling the simple pores of many Marchantiaceae. 
1 Leitgeb, l.c., iii. p. 126, PI. IX, Figs. 16=19. 
