118 BOTANICAL GAZETTE [FEBRUARY 
The large air cavities prevent the penetration of the fixing fluid, 
to overcome which the pieces were submerged by means of cotton 
plugs. After dehydration the material was passed through chloroform — 
into paraffin. Sections were stained with the triple stain of Flem- 
ming or with Heidenhain’s iron-alum haematoxylin. 
SEXUAL ORGANS. 
Young antheridia were found in October. They begin to develop 
while the plants are young and growing on soil not supplied with a 
large quantity of water, although the conditions for vegetative growth 
are good. At this time the thallus is ribbon-shaped, with a thick- 
ened apical end and a longitudinal median groove, the thallus in 
cross-section having about the shape of an inverted Y with a ridge 
of tissue between the arms (fig. 9). Very few plants are found 
which do not produce antheridia. The archegonia develop later 
in the same thallus. At first there seemed to be in this a distinction 
between Riccia lutescens and Ricciocarpus natans, because Ricctocar- 
pus natans has been described by SCHIFFNER, LEITGEB, and CAMpP- 
BELL as being strictly dioecious, but the work of GARBER shows 
conclusively that it is monoecious. The earlier observers state that 
Ricciocarpus fruits in autumn, so it seems probable that their material 
was collected after the older portion of the plant had decayed, leaving 
only the portion bearing sporophytes. 
The antheridia are produced in acropetal succession in three to 
five rows (figs. 10, IT). 
The antheridium develops as has been described for other species 
of Riccia. A superficial cell on the floor of the dorsal furrow just 
back of an apical cell protrudes above the surface and is cut off by 
a horizontal wall. The outer cell increases in size, and is divided 
by three or four cross walls, then a longitudinal wall is formed divid- 
ing the young antheridium into two equal parts: this is followed 
by a second longitudinal wall perpendicular to the first. Then 
periclinal walls are formed which cut off the single layer of cells 
which form the wall of the. antheridium. The cells in the center 
now undergo repeated divisions until a very large number of cells 
is formed. Each of these cells is almost. cubical in form and in 
Riccia has been described as producing a single spermatozoid, 
