New and Little Known West-Himalay an Liverworts. 317 
tinuation of growth after the formation of the female receptacle. 
It resembles Exormotheca in the position of the male and female 
receptacles, the number and position of the involucres in the carpo- 
cephalum, and to a certain extent the structure of the sporogonium. 
The latter, however, is much simpler in Stephensoniella , as is shown 
by the thickening on the wall-cells of the capsule and the elaters. 
Stephensoniella differs from the genus Exormotheca in its simpler 
sporogonium, empty air-chambers and, above all, in the continuation 
of growth after the formation of the female receptacle. This last 
feature coupled with the simple sporogonium is extremely interesting 
as it points out the way in which forms like Corsinia and Boschia 
have originated. Indeed, Stephensoniella is a connecting link between 
Exormotheca on the one hand and Corsinia and Boschia on the other. 
Its resemblance to the latter is seen in several features. The 
male receptacle in the two is similar. Secondly, the female receptacle 
of Boschia may be derived from Stephensoniella by supposing that 
the dichotomy of the primary female branch does not take place and it 
may be compared to the condition found in Targionia. The structure 
of the capsule wall and the elaters is very much alike in Boschia 
and Stephensoniella. Of course, it is not meant that Boschia has 
descended directly from Stephensoniella by suppression of the 
dichotomy but it must have descended from some similar ancestor. 
Similarly, Corsinia , though further reduced, must have come from 
some similar ancestor with a large number of involucres. It has 
been mentioned that the involucres of Stephensoniella are only 
formed if the archegonia are fertilised. Similarly the protecting 
scale of Corsinia only develops after fertilisation. If only a single 
sporogonium is produced it remains simple, equivalent to a single 
involucre ; but if several sporogonia are produced it becomes lobed, 
that is, equivalent to several involucres. 
The origin of forms like Riccia may be considered here. Un¬ 
fortunately there is no great evidence on which one may decide the 
question. Goebel’s view that Riccia may be derived from forms 
like Targionia, which he would put in the Simplices, seems to be 
very probable. The chief fact bearing on the question is the 
arrangement of the archegonia in some of the Ricciaceae in median 
dorsal rows. This condition would be reached if the apical growing 
point of aform like Targionia, instead of being displaced downwards, 
were to go on growing forwards, along with the total reduction of the 
involucre. It must be noted, however, that there is a great gap 
between Riccia and Targionia as regards the structure of both the 
* fl 
gametophyte and the sporophyte generations. 
