elviii Proceedings of the Asiatic Society of Bengal. {N.S., XV, 
In some species of Plagiochasma examined by the writer it has 
been found that the pores on the female receptacle are barrel- 
Shaped while those on the male receptacle are simple. Inter- 
preted with the help of the principle enunciated above it means 
that the latter forms are reduced. We shall presently see that 
this conclusion is confirmed by other considerations also. In 
other forms like Exormotheca and Stephensoniella the pores 
are simple on the receptacle as well as the thallus. These forms 
would thus represent a still lower stage in the series. Lastly 
we come to the forms where there are no definite pores at 
all, as in the genus Riccia 
It is interesting to note that in some species the stomata 
are altogether lost, at least sometimes, while in others a ten- 
dency in this direction is distinctly visible. Cyathodium tubero- 
sum, 
since then sent to him from other parts of India also, often pos- 
sesses no stomata in the sterile plants. In a plant recently sent 
to the writer by Professor Fyson from South India and ‘which 
will have to be referred to a new genus, the thallus is very long 
d narrow and possesses no stomata in the greater part of its 
length and dey only occur in its anterior part. In both these 
cases, however, air-spaces are present in the interior of the thal- 
lus. In the South-Indian plant the spaces in the posterior part 
a very small, suggesting that they are gradually being elimin- 
a 
Another important point is the position of the receptacles. 
In the higher forms the male and female organs are found in 
groups on stalked receptacles which are usually terminal. In 
other forms they are dorsal. The stalk of the terminal recep- 
tacle is in direct continuation of the midrib and in the highest 
type, Marchantia, it possesses the typical pores and air-cham- 
bers on the dorsal side while it bears scales ventrally. It is, 
therefore, generally admitted that the stalk is a direct upward 
continuation of the thallus i in these cases and the lobes of :the 
receptacle represent the branches of the thallus. On account 
of the dorsal position of the stalk in some genera, like Plagio- 
chasma and Clevea, Leitgeb considered that the stalk of the 
latter genera is a mere dorsal outgrowth and not homologous 
with the stalk of the higher forms. The case of Preissia com- 
mutata in which a terminal stalk becomes dorsal by the further 
growth of the thallus had been long known but on account of 
e groove on its anterior side it did not lead him to consider 
that the dorsal position of the stalk in the other genera might 
secondary. Apart from the plausibility of this view on 
purely a priori grounds it has been shown by the tid that in 
Plagiochasma articulatum the stalk is terminal at first and be- 
comes dorsal by the further growth of the thallus. "The dorsal 
position is therefore secondary. The dorsal position of the 
stalk is arrived at similarly in the genus Stephensoniella des: 
