176 BOTANICAL GAZETTE. [ July, 
The act of dehiscence of the sporangium was observed in 
six cases. The rupture begins near the apex, a little toward 
the ventral surface. The opening is at first irregular, with 
radiating lines extending between surrounding cells; but 
soon the dehiscence takes a definite direction between two 
rows of transverse cells—this being the place where the wall 
is thinnest, and the line between adjacent rows of external 
cells straightest. The line of dehiscence in its descent to 
the base frequently passes from one side of a row of trans- 
verse cells to the other side. Near the apex especially the 
dehiscence is usually quite irregular, as shown in fig. 2. 
What is the function of the transverse cells? It can not 
be merely to pull the wall apart; this is accomplished ina 
greater degree by the oblique and longitudinal cells. The 
transverse cells prevent the ventral wall of the sporangium 
from shortening equally with the dorsal wall—thus assisting 
in dehiscence and causing the edges of the open sporangium 
to gape widely. 
Ill. Structure and action of the elaters.—The external 
coat of the spore divides at maturity into four narrow, spira 
bands—the so-called elaters—as shown in fig y. If the 
‘rom end to end, a very thin bit of membrane attached by 
one edge to the elater (fig. 8). This piece of membrane has 
ae of having been peeled off the surface of the 
