THE MARCHIANTIACEAE OF SINSINAWA MOUND. 223 
the time of the fertilization process of this species. Probably 
most of the zygotes are formed by the first of July. Reduction 
division takes place in the spore mother cells of Conocephalum 
conicum in the early part of September?‘ and the fully de- 
veloped spores begin to germinate within the capsules late in 
September or early in October, and continue cell division until 
the eight-celled stage is reached. Here they rest until spring, | 
when cell division is resumed and continues until the thirty-to 
forty-celled stage is reached. Simultaneous with the last of 
the intra-capsular divisions of the young sporelings, the stalk 
of the carpocephalum and the foot and seta of the sporophyte 
elongate rapidly by the growth of their cells. The sporelings 
are disseminated about the twentieth of April. One usually 
can not find sporophytes intact after the first of May. 
The discharge of the spermatozoids of Preissia commutata, 
quite unlike those of Marchantia polymorpha and Conocepha- 
lum conicum, does not occur until October. There is some devel- 
opmentof thesporophytesin the fall, but there is little differ- 
entiation of sporogenous cells until the following spring. With 
the opening of spring, the sporophytes develop rapidly, so that 
the tetrads and, sometimes even the mature spores and elaters, 
are dispersed as early as April twentieth. Spore dispersal is 
usually complete by May tenth. The present year, is, never- 
theless, a notable exception to the general rule, as the season 
has been usually late, particularly so in that locality. The 
tetrads were not formed earlier than May tenth this year. 
Since the principal part of the development of the sporophyte 
of Preissia commutata occurs in the early spring, this plant is 
particularly affected by a late season. The spring activities of 
Conocephalum conicum and Marchantia polymorpha appear 
to be less retarded, although fertilization in the latter form 
will probably be considerably later this year. 
It is somewhat interesting to note the rather short period 
between fertilization and spore dispersal in Marchantia poly- 
morpha as compared with the corresponding, very long periods, 
almost ten months, in Conocephalum conicum and, between 
seven and eight months, in Preissia commutata. The season 
* for collecting spores and elaters in each of the three plants is 
