1921] HAUPT—REBOULIA 69 
antheridial stalk as 1-celled, slightly elongated structures with a 
nucleus and a highly vacuolated cytoplasm (figs. 9-13). They 
elongate considerably and secrete abundant mucilage around 
the mature antheridia. 
3 ARCHEGONIUM 
The archegonia are borne on receptacles which arise as dome- 
like areas at the growing point of the thallus. The formation of 
the archegonial receptacle involves the apical cell of the thallus, 
so that growth for the season is checked. Several (up to 6) growing 
points are organized in the 
young receptacle from seg- 
ments of the main apical cell 
of the thallus, and thereby a 
new apical cell is formed in 
each receptacle notch. 
In the simpler Marchan- 
tioideae, as in Clevea and. 
Aytonia, the main apical cell 
of the thallus is not involved 
in the formation of the arche- 
gonial receptacle, so that 
several successive groups of Fic. 13.—Completion of periclinal wall 
archegonia may be formed on formation in young antheridium, X790. 
the same thallus, or, as Miss 
STARR (8) has reported in Aylonia, an antheridial receptacle may 
follow the formation of an archegonial receptacle. Thus in these 
forms th gonial receptacle represents a simple dorsal upgrowth 
of the thallus. In Fimbriaria and Grimaldia Le1tcEB has shown 
that the apical cell is involved in the formation of the archegonial 
receptacle, and this is the situation in Redoulia. In the higher 
Marchantioideae this condition prevails, and further advance is 
shown merely by the greater production of archegonia over a 
longer period, and the formation of a long receptacle stalk earlier 
in the life history of the archegonia. 
The archegonium initials arise from the third or fourth segment 
of each apical cell, and do not appear until the young receptacle is 
conspicuously dome-shaped. LerrrceB figures a very young 
