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AMERICAN JOURNAL OF BOTANY 
[Vol. 9. 
rounded by a groove within which small narrow scales develop, similar to 
those around the female receptacle. Mucilage cells arise from the base of 
the antheridial chamber (figs. i6, 19). Usually the receptacle is raised 
only a slight distance above the general surface of the thallus (fig. 13), but it 
may, in some cases, be elevated on a short stalk (figs. 14, 15), the stalk 
being formed by intercalary growth of the ventral tissue forming a central 
core surrounded by air-chamber tissue like that of the thallus itself. The 
fungal hyphae of the compact tissue may penetrate the stalk, and in one 
case the raised portion bore a few ventral scales and a few pegged rhizoids on 
the posterior margin (fig. 14). 
Figs. 13-15. Vertical longitudinal sections through the receptacles. Figure 13 
shows two male receptacles (d^) and the female receptacle ( 9 ), the male receptacles being 
sessile, as usual. Figures 14 and 15, male receptacle raised on a short stalk. Figure 14 
shows the fungus-infected area (indicated by dotted lines) extending into the stalk, as well 
as small ventral scales (sc) and pegged rhizoids (rh) on the posterior margin. X 28. 
Bisexual Receptacles. Bisexual receptacles are not commonly found in 
the higher Marchantiales. They have been known for a long time in 
Chomiocarpon (Preissia), where they occur rather frequently, as the writer 
has found. They were first reported in Dumortiera irrigua by Taylor (27), 
and later for two other species, D. trichocephala and D. vehitina, by Ernst 
(12). Monoselenium tenerum, as reported by Goebel (14), and occasionally 
certain species of Marchantia, according to Cutting (9), complete the list 
to date. The writer has found a few such cases in Reboulia, where arche- 
