133 



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 Rieeias 

 described. 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 hepatics. 



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 Avails 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. 



COXCI/USIOX:-. 



Botanists recognize two distinct forms of R. fiuitans, 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 archegonial pit, are not 

 generally scattered by the elements, and vary much in size. 



