36 
BOTANY: D. H. CAMPBELL 
THE MORPHOLOGY AND RELATIONSHIPS OF PODOMITRIUM 
MALACCENSE. (STEPH.) 
By Douglas H. Campbell 
DEPARTMENT OF BOTANY. LELAND STANFORD UNIVERSITY 
Presented to the Academy, October 30, 1914 
There are but two species of the liverwort, Podomitrium , P. phyl- 
lanthus, a common species of the Australian region, and P. malaccense, 
which according to Stephani is known only from Singapore and New 
Caledonia. The writer collected the latter species in Sarawak, Borneo, 
in February, 1913, and also at one station in Luzon, in May of the same 
year. The plant is common in Sarawak, and sufficient material was 
secured to make a pretty complete study of its structure, which has not 
been done before. 
Podomitrium is often included in the genus Hymenophytum, but it 
is certainly generically distinct. 
The sterile plants of P. malaccense resemble exactly certain species 
of Blyttia, and the plant can only certainly be recognized when it bears 
the reproductive organs. Fertile plants, however, are immediately 
distinguishable by the position of the reproductive organs, which instead 
of being borne on the dorsal surface of the ordinary shoots, are formed 
upon the special branches which grow from the side of the midrib upon 
the ventral side of the main shoot, very much as in Metzgeria. 
As in Blyttia, the thallus has a very conspicuous, and sharply de- 
limited midrib, and wings which consist of a single layer of cells. In 
P. malaccense, the thallus is usually unsymmetrical, one of the wings 
being almost obliterated. Rather short rhizoids occur upon the ventral 
side of the midrib, but these are not uniformly distributed. They occur 
in dense patches separated by considerable intervals which are quite 
free from rhizoids. 
In the form of the apical cell, and in the character of the thick-walled 
cells which occupy the axis of the midrib, Podomitrium closely resembles 
Blyttia. 
The fully developed plant may reach a length of about 4 cm. 
with a maximum width of about 4.5 mm. No cases of dichotomous 
branching were seen, all of the branches appearing to be of adventitious 
origin, springing like the sexual shoots from the sides of the midrib. 
The antheridia arise in somewhat irregular rows, one on each side of the 
midrib of the special shoot upon which they are borne. They arise in 
acropetal succession, and each is covered by a scale with laciniate margins. 
