122 MCALLISTER: MORPHOLOGY OF THALLOCARPUS 
antly supplied with chloroplasts while the inner layer lacks them 
(Fics. 11,12). As the spores mature the inner of the two layers 
of venter cells is crushed and absorbed while the outer layer re- 
mains intact, forming a persistent layer about the mass of spores 
(Fic. 14). 
The cells of the sporophyte are probably more than half grown 
before any difference is perceptible between the cells of the 
amphithecium and the sporogenous cells (FIG. 9). This difference 
is first seen in a decrease of the protoplasmic content of the 
peripheral cells, and a possible increase in the density of the proto- 
plasm of the sporogenous cells (Fic. 10). Later, as the sporo- 
genous cells continue to enlarge, a difference in the size of the 
cells is apparent. At the time of the rounding up of the spore 
mother cells before division, the cells of the peripheral layer have 
a very scanty protoplasmic content and small, degenerate nuclei. 
The cells are however plump and distended with cell sap and do 
not show signs of collapse till much later (Fic. 12). Their col- 
lapse and disintegration at a later stage greatly enlarges the 
cavity in which the spores lie (Fic. 13). 
Beer (4) has observed similar, large, vacuolate cells making up 
the amphithecium of Riccia glauca L. Garber (7), Campbell (6), 
and Lewis (9) have, however, described the amphithecium of 
Riccia as made up of flat cells which have dense contents. 
The rounding up of the spore mother cells previous to the 
reduction divisions is accompanied by a swelling and gelatinization 
of the cell walls (Fic. 12). The gelatinous material accumulates 
in the spaces between the now rounded spore mother cells (Fic. 13) 
where it interferes greatly with the penetration of the killing 
solutions. In fixed material it stains deeply with the violet stain. 
Garber and Lewis have both observed such gelatinous accumula- 
tions in Riccia and are of the opinion that it is food material, 
derived, in part at least, from the surrounding cells, which are 
believed to be abundantly supplied with food material. In 
Thallocarpus this is not the case. No excess of food is to be 
identified in the surrounding cells nor is there any marked change 
in these cells upon the appearance of the gelatinous material. 
The gelatinization of the walls of the spore mother cells together 
with the disintegration of the wall layer of cells seems sufficient 
to account for the amount of gelatin formed. 
