1904] JOHNSON—MONOCLEA 199 
as a reduction due to the nature of the habitat of Monoclea. For, 
though these plants are not actually submerged, they do live in very 
wet places and are surrounded by a constantly saturated atmosphere. 
COKER (’03) has shown that we have an actual example of this sort 
of reduction in Dumortiera hirsuta, plants of which growing in a 
damp atmosphere on a porous, sandy soil, had well-developed air 
chambers, while other plants which were constantly wet with dripping 
water had no trace of such chambers. Even in Marchantia I find 
that, as was shown by RUGE (’93), submerged plants have imperfect 
air chambers or none at all. There seems also to be a marked reduc- 
tion in the size of the ventral scales, in the number of tuberculate 
thizoids, and likewise in the number of tubercles in them in these sub- 
merged plants. 
The facts of vegetative structure referred to strongly indicate a 
relationship with the Marchantiaceae, and the structure and develop- 
ment of the reproductive organs seem to me to confirm this beyond 
reasonable doubt. 
The male receptacle of Monoclea does not, it is true, closely 
resemble that of Fegatella, with which it has been most frequently 
compared, since it has but one growing point, while that of Fegatella 
has several, as has been shown by LEITGEB (’81, p. 95) and CAVERS 
(04). In this respect Monoclea resembles much more certain other 
genera of the Marchantiaceae. In Corsinia, for example, according 
to Bischorr (35, pl. 70) and Lerrcrs (’79, p. 48), the antheridia 
“rise acropetally on an elongated, thickened, and bordered receptacle 
very like that of Monoclea in origin and structure. Similar also are 
€ less known male receptacles of Funicularia, according to Mon- 
TAGNE (’56), and of Sauteria, according to Biscworr (’35) and LErr- 
Hod (81). Among the higher Marchantiaceae also male receptacles 
Senilar to that of Monoclea are not wanting. Thus Aytonia (LEITGEB 
7 GOEBEL ’98), Reboulia (BiscHorr ’35, Lerrces ’81), Grimaldia 
SSCHORF 735, LEITGER 81), and especially Fimbriaria (BISCHOFF 
* CAMPBELL ’9 5) show a striking resemblance to Monoclea in the 
mcture and development of the male receptacle. On the other 
Rory ie is no structure closely comparable with the male recep- 
The de onoclea known among the Jungermanniaceae. 
velopment and structure of the sunken antheridia of Mono- 
