1919.] The Siath Indian Science Congress. elvii 
state, and the boundaries of the chambers are indicated by 
reticulations on the dorsal surface. Similar reticulations, but 
more faint, are met with some distance behind the apex in 
D. hirsuta also, but the surface is otherwise perfectly smooth 
in this species and in D. trichocephala. As a matter of fact we 
can trace all the stages in the process of reduction in different 
genera according to their more or less aquatic habit. Preissia 
commutata, occurring on moist soil, shows the typical structure 
h Ss an aments. 
of the higher forms with air-chambers, pore 
I 
Fegatella. The species of Dumortiera show the remaining 
ter 
mooth at maturity. 
This interesting series showing the reduction of the air- 
chamber layer is however only a special case, as it is due to 
the presence of a special factor, the aquatic habit, and I would 
not have alluded to it if this were the only point illustrated by 
this genus. For, however clear this phenomena may be in this 
particular case it cannot be made the basis of a general con- 
clusion regarding the whole group to which these genera be- 
The other interesting point in this genus has been 
observed quite recently by the writer. Both in D. hirsuta 
where the air-chamber layer is confined to the apex and the 
cells anywhere on the thallus, papillate cells are met with on the 
female receptacle. Here we have an illustration of the well- 
The pores in the higher forms of the Marchantiales are 
barrel-shaped both on the thallus and the receptacles. This is 
the case, for example, in the genera Marchaniia and Preissia. 
In certain forms which are undoubtedly lower as judged by other 
characters, e.g. Fegatella, Reboulia, etc., the pores are barrel- 
shaped on the receptacles but those on the thallus are simple. 
