STEVENS: DISCOID GEMMAE IN LEAFY HEPATICS a6d 
One of these quadrants in each half usually grows more rapidly 
than its sister cell and thus displaces the wall separating them, so 
that each half of the gemma soon consists of two unequal cells 
symmetrically placed with respect to the median wall (Fic. 1, C). 
Each of the larger cells then begins to function as a two-sided 
apical cell (FIG. 1, D and E) and cuts off three segments, the first 
by a wall approximately parallel to the median wall. Each seg- 
ment in turn divides by a periclinal wall and the outer cell of the 
first segment divides further by an anticlinal wall. Each of the 
DEOE 
Ficure1. A-F. Cololejeunea Biddlecomiae. A-E. Gemmae in various stages of 
development, X 600. F. A gemma about ready to separate (x, apical cell), X 600 
G. Cololejeunea calcarea. A gemma in which the basal and apical quadrants are 
nearly equal, 
smaller, or basal, cells also divides regularly. The cell divisions 
normally take place exactly as they do in the first apical segment, 
so that each basal portion of the mature gemma contains three 
cells (FIG. 1, D and E). Occasionally, however, one of the outer 
cells divides again by a periclinal wall (Fic. 1, F). 
The gemmae increase in size somewhat, after cell division has 
ceased, by the growth of the cells themselves; and this growth 
continues, for a time, after the gemmae are shed. This is clearly 
shown by the fact that the gemma, at the time it is shed, is about 
0.035 mm. in diameter, while it is common to find gemmae loose 
