495 
Geothallus tuberosus , Campbell. 
was more or less wedge-shaped, but often nearly orbicular in 
outline. The plants were growing crowded together, and 
almost buried in the earth, and as they were beginning to dry 
up were not at all conspicuous and, as already said, were quite 
overlooked at first, and it was not until the moisture with 
which they were supplied started them into growth that 
attention was called to them. These plants were about 
5 to 7 mm. in length by 3 to 4 mm. in breadth, and often 
quite unbranched, or only once dichotomous. The plants 
raised in the laboratory were usually somewhat larger than 
the original ones, and branched more freely. This greater 
vigour, as well as the more luxuriant development of the 
leaves, was no doubt owing to the great amount of moisture 
furnished them. The branching in all cases was a typical 
dichotomy like that found regularly in the thallose Liver- 
worts. 
In connexion with the freer branching and better develop- 
ment of the leaves of the plants grown under glass may be 
mentioned a similar acceleration of growth in Sphaerocarpus . 
A number of specimens of Sphaerocarpus terrestris var. call- 
fornicus Aust. appeared in one of the cultures of Geothallus , 
and these differed so much from the normal plants as to 
be scarcely recognizable. They grew very vigorously and 
decidedly exceeded the normal plants in size. This was 
especially true with the male plants, which were several times 
larger than is usually the case. They branched freely, and 
developed unmistakable leaves, not unlike those of Geothallus , 
while the normal plants have the margin of the thallus quite 
undivided l . 
The thallus of Geothallus is fastened to the earth by very 
numerous white rhizoids. These are outgrowths of superficial 
cells, and are thin- walled and colourless like those of most 
J ungermanniaceae. 
In regard to the arrangement of the leaves, Geothallus 
resembles most nearly Fossombronia among the American 
1 For particulars concerning these abnormal specimens of Sphaerocarpus , see 
a recent article by the writer in Erythea, May, 1896. 
