June, 1922] 
DUPLER REBOULIA HEMISPHAERICA 
Marchantia and Chomiocarpon, the dorsal position being due to the very 
early appearance of the adventitious branch. The male and female recep- 
tacles, according to this, are morphologically equivalent, Goebel holding 
that receptacles of different morphological nature are improbable on the 
same plant. Voigt (28), Leitgeb (21, 22), and Cavers (7) all found female 
receptacles in Reboulia in a median dorsal position behind the apex, condi- 
tions giving support to the homology of the two receptacles, despite the 
abnormahty of such a position of the female receptacles. Evans (13), 
discussing the homology of the female receptacle in Plagiochasma and 
Reboulia, says: 
The mere fact that the growing point is not carried upward by the elongating stalk 
(in Plagiochasma) does not invalidate the homology of the carpocephalum with that of 
Reboulia. 
His conclusion could be applied to the male receptacle as well. Haupt 
(16) finds the activity of the apical cell unchecked in the formation of the 
disc and apparently holds to Leitgeb's view. 
It was shown above that the disc may be elevated on a short stalk 
which may, in rare cases, bear scales and pegged rhizoids. The presence 
of one or more growing points on the young receptacle is evident, as well 
as is the formation of apical cells on the disc independent of the apex of 
the thallus (fig. 30). The writer is inclined to the view that in the male 
receptacle of Reboulia we have a possible elementary stage of a branch 
system, representing a transition from the "dorsal outgrowth" to the 
"composite" form, or vice versa if one were to insist on a reduction series. 
Reboulia is sufficiently plastic to give several phases of the transition, as, 
for example: the thallus apex may be unchecked, the sessile male recep- 
tacles frequently dorsal, the female receptacle occasionally dorsal; the 
growth of the thallus may be checked temporarily by the formation of the 
male receptacle, an innovation shoot growing out with a narrow base, 
giving the jointed aspect of the plant sometimes figured, as by Goebel (15) ; 
the thallus apex may be permanently checked, being used up in the forma- 
tion of the male receptacle, which remains as a sessile structure (as in 
Lunularia and Conocephalum) ; and, rarely, the male receptacle may be 
elevated on a short stalk (figs. 14, 15). The marginal male receptacles, 
as found by C. and R. Douin (10), and the occasional clusters (figs. 3, 4) 
can be explained as due to intercalary growth following the forking of the 
disc, thus separating the several points of origin from one another. 
Conclusion 
On the whole it seems to the writer that the male receptacle and the 
antheridium of Reboulia suggest a very plastic and significant condition 
from a morphological standpoint, being primitive in some features and 
suggestive of higher forms in others. 
