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gonial pore, much the same as a similar structure does in Pellia. Stoma each 
being surrounded by four cells open into deep air chambers. 
The thallus develops from one or more apical cells as do other Riccias 
deseribed. This is a large triangular cell in longitudinal section, situated 
at the forward end of the growing thallus. The thallus is only three or four 
cells thick beneath the dorsal furrow. In section air chambers appear very 
large and numerous. They develop probably in three ways: (1) by internal 
splitting; (2) by the parting of cell rows for long distances; and (3) by the 
process so well described by Leibgeb for the hepaties. 
The sex organs develop in general in the same way as described for other 
liverworts. The mature archegonium consists of two base cells, ventral and 
neck cells, four cover cells, four neck canal cells, ventral canal cell and an 
egg. The funnel-shaped mouth of a mature archegonium opens often just 
below the pore of a mature antheridium or recurves away from the growing 
point. This is a fine adaptation to catch the sperm as they come from the 
antheridium. 
The antheridium consists of a stalk, a sterile coat of tabular cells, and 
a mass of deeply staining cubical cells. It never protrudes above the surface 
of the thallus but lies buried deeply in the thalloid tissue. 
The sporophyte develops rapidly. In its early stages it is oval but as it 
matures it becomes spheroid. The sporogenous tissue round off and tetrads 
“are produced in the usual manner. The mature spore varies much in size, 
being 75-90 microns wide. Its outer surface is deeply areolate, the other 
faces being less areolate. Three distinct walls can be seen in cross-section, 
an inner wall that does not stain well, a middle deeply-staining wall, and an 
outer which seems to separate readily. The nucleus containing a distinct 
nucleolus is small. Starch and oil are stored throughout cytoplasm. 
CONCLUSIONS. 
Botanists recognize two distinet forms of R. fluitans, a terrestrial and an 
aquatic form. It seems very doubtful if the aquatic ever changes into the 
terrestrial and fruits as observers have portrayed, but always reproduces 
vegetatively. 
The thallus, sex organs, and sporophytes develop in general as described 
for other liverworts. The spores remain within the archegoniai pit, are not 
generally scattered by the elements, and vary much in size. 
