158 
F. Cavers. 
to the dorsal side of the receptacle itself—not centripetal, as is 
often erroneously stated. In the disk-like male receptacle of 
Marchantia and Preissia , the antheridia do not undergo this inversion, 
and the radiating centrifugal arrangement of these organs is at once 
evident. 
In his “ Composite,” Leitgeb placed the genera Lunularia, 
Dumortiera, Preissia, Marchantia, and (doubtfully) Fegatella. The 
remaining genera of Marchantiales with stalked carpocephala which 
were known to him were divided into two groups which he named 
“Astroporae” ( Clevea, Sauteria, Peltolepis) and “ Operculatae ” 
( Plagiocliasma , Reboulia, Grimaldia, Neesiella, Fimbriaria). In these 
two groups, and also in Fegatella, the female receptacle was believed 
by Leitgeb to be in all cases merely a dorsal outgrowth of the 
thallus, the archegonia being developed singly on the periphery of 
the receptacle and each archegonium becoming enveloped by its 
own involucre; except in Clevea and Plagiocliasma, however, the 
stalk of the receptacle has either a single furrow or two furrows, 
and this was taken by Leitgeb to indicate that the apex of the 
thallus entered into the formation of the stalk but not into that of 
the archegonium-producing region itself. The carpocephalum was 
therefore regarded as representing a single branch, the apex being 
used up in its development, whilst the “Composite” carpocephalum 
was interpreted as being composed of a branch system. Although 
the distinctions upon which Leitgeb founded this classification of 
the Marchantiaceae can no longer be maintained, it will be convenient 
in this resume to deal with the genera in three groups, corresponding 
with Leitgeb’s “ Astroporae,” “ Operculatae,” and “ Compositae.” 
I.—Astroporae. 
Leitgeb named this group from the fact that the radial walls of 
the cells (arranged in a single ring) surrounding the thallus air-pores 
are as a rule strongly thickened, giving the pore a star-like appearance 
in surface view. Apart from the presence of exactly similar pores 
in other families ( e.g ., in Tessellina and some species of Plagiocliasma), 
there are several species of Clevea in which this thickening does not 
occur. However, there is no doubt that the three genera—to which 
a fourth ( Gollaniella ) has recently been added by Stephani (62) for 
a Himalayan plant allied to Clevea — form a natural group. Their 
geographical distribution, which presents some very nteresting 
features, has been described by Solms-Laubach (59). The writer 
found representative species of all three genera ( Clevea hyalina, 
