1904] GARBER: RICCIOCARPUS NATANS 169 
So far as I know, the observation of the phenomena of fertili- 
zation in a liverwort has been recorded only for Riella, studied 
_ by Kruch (9). He was, however, unable to get stages of actual 
fusion of the nuclei. With the entrance of the sperm, marked 
changes begin both in the egg and in the surrounding tissues. 
The oospore develops a cellulose membrane and quickly enlarges 
so as to fill completely the cavity of the venter. The cells of 
the venter begin dividing by walls parallel to the surface and 
make a complete double layer before the first division of the 
fertilized egg. A two-layered calyptra seems to be the rule 
among Ricciaceae, but as many as four layers occur among the 
Marchantiaceae. 
THE SPOROPHYTE. 
The first division in the sporophyte is usually transverse 
(7g. 27), but it may be oblique (fig. 28). The next wall may 
appear first in either the epibasal or hypobasal cell, and may be 
perpendicular to the first wall, thus forming a quadrant, or may 
be parallel to it, producing a row of four cells (fig. 30). Divi- 
sions then occur in all directions, producing a mass of thirty or 
forty cells, after which the amphithecium becomes distinguish- 
able as a regular layer enclosing the spore-producing cells. 
Further divisions, not simultaneous (fig. 32), produce approxi- 
mately four hundred spore mother-cells. 
Up to this point the sporophyte has been a solid mass. Now 
the calyptra and amphithecium expand, leaving the spore mother- 
cells free, rounded, and separated from one another. At the same 
time there is excreted from the surrounding tissues a large quantity 
of nutritive material which fills the spaces around the mother- 
cells, giving them the most favorable conditions for rapid growth. 
Most of this nutritive material is absorbed by the spore mother- 
cells as they rapidly enlarge to fill again the amphithecium, and 
the remainder is pressed into thin plates adhering to the surface 
of the tetrads of spores (fig. 38). 
The inner layer of the calyptra collapses shortly after the 
formation of the tetrads. The outer layer persists, while the 
amphithecium is distinguishable until the spores are almost 
tripe. All of the spore mother-cells produce spores, with no 
