3096 : BOTANICAL GAZETTE [DECEMBER 
The line of distributive succession is not easily shown in L. 
lucidulum, but a case of L. obscurum was found that well illustrates 
the idea. A sporeling of this species was found that was 1o cm. 
long, bearing six successive aerial branches and a distinct foot at 
the end of the underground trailing stem. The sporeling grew on 
the top of a small knoll, but instead of staying there, it took the | 
shortest path toward the bottom, where adult sporophytes were 
growing in a moist hollow. 
The réle of prothallia in the life history of L. lucidulum is of 
slight value to the species, therefore, once a colony is firmly estab- 
lished. But for the opening up of new localities, and therefore for 
the geographical distribution of the species, the gametophyte plays 
the important part of getting a foothold in regions too unfavorable 
for vegetative parts, especially gemmae, to flourish. The sporeling 
itself rarely reaches maturity. 
Two facts were observed in the collection of prothallia of various 
species which seemed to indicate that some agent other than wind 
takes part in the distribution of spores. The first of these was that 
the prothallia, in nearly all species, occur in bunches. The second 
was the frequent occurrence of prothallia in groups of four. The 
latter condition is explained by supposing that the original group 
of tetraspores was distributed bodily, and that the four germinated 
simultaneously. This phenomenon was observed very frequently 
in L. clavatum, L. complanatum, and L. lucidulum, most frequently 
in the first. 
At the time of the shedding of spores the tetrasporic group is 
broken up, so that it does not seem probable that these groups are 
distributed by the wind. The only other explanation which sug- 
gests itself is that portions of the plant bearing sporangia are 
carried away by animals. The appearance of patches of prothallia 
and sporelings strongly suggests this. An isolated sporeling or 
gametophyte is rarely found. 
HABITAT 
Many searches for prothallia have been futile, not so much 
through a paucity of material as through a failure to learn, by a 
process of elimination, the exact type of terrain in which they grow 
