224 Shiv Ram Rashyap. 
maturity. It opens by the separation of a part of the apex irregularly. 
The chief characters of the genus Aitchisoniella may be briefly 
summarized thus. Thallus of the type of the Astroporeae, i.e., with 
narrow chambers in one or two layers and pores with one ring of 
cells having slightly thickened radial walls ; scales in two rows with 
terminal filamentous appendages; antheridia in two rows along 
midrib, imbedded in the thallus, behind the female receptacle ; 
female receptacle terminal, lateral or in the fork between two 
branches, sessile, consisting of one or two involucres joined to the 
thallus by a stalk-like constriction ; dorsal tissue of receptacle 
continuous with dorsal tissue of thallus; capsule included with a 
well developed foot; cells of the capsule-wall with thick annular 
and spiral bands. 
It is obvious that the genus Aitchisoniella must be placed near 
Targionia. Although the structure of the thallus has some 
resemblance to that of the thallus in the Astroporeae, the involucre, 
the group of archegonia in each involucre, the capsule-wall 
and to a less extent the ventral scales at once suggest its 
affinities with Targionia. The receptacle in Aitchisoniella may bear 
one involucre or two. In this respect it is midway between Targionia 
and Exormotheca. If we suppose the female receptance of Exormo- 
theca to become sessile we should have a structure like the female 
receptacle of Aitchisoniella with the difference that the involucres in 
the latter are not directed so distinctly laterally as those of the former. 
But this difference can be easily understood by the absence of the 
peduncle, the small amount of the receptacle-tissue and the stoppage 
of growth soon after dichotomy. This resemblance between 
Aitchisoniella and Exormotheca is further increased if we take into 
account the position of the female receptacle in the two. We can 
thus arrange the three genera in a descending series taking into 
consideration the structure and position of the female receptacle 
which is admittedly the most important character for classification: 
(1) Exormotheca , (2) Aitchisoniella , (3) Targionia. 
But it might be asked, why should we not arrange them in an 
ascending series ? This, however, cannot be maintained. Apart 
from the arguments advanced by Goebel after his study of Mono- 
selenium, the writer has strong evidence in the structure of Stephen-- 
soniella and Plagiochasma articulatum, which will be described later^ 
that there has been a wholesale reduction in the Marchantiales. 
At present it is sufficient to call attention to the facts in connection 
with the male receptacle of Cyathodium tuberosum. This genus is 
