330 WILLISTON: DISCOID GEMMAE IN RADULA 
Toward the periphery they decrease gradually in size, those at the 
very edge averaging about 0.01 mm. Gemmae occur in this species 
on leaves of vegetative branches (FIG. 3), on male bracts (FIG. 1), 
on the margins of old perianths (ric. 2), and on other gemmae 
(FIG. 4). Gemmae occurring on leaves or bracts were most 
numerous along the acroscopic margins, and in no case were gem- 
mae found on the lobules of the leaves. There is apparently some 
relation between the stage of development of a vegetative branch 
and its capacity to produce gemmae, for the gemmae are rarely 
4 
3 
Ficures 1~4, Radula flaccida. 1, male bracts and prolifera’ 
branch bearing gemmae, X266. 2, old perianth bearing gemmae, 
vegetative leaf with gemmae, X 266. 4, small gemmae growing on the mae 
mature gemma, X66. 
tion of antheridial 
66. 3 normal 
of a 
nd 
found on young plants. The fact that gemmae are never fou 
on the youngest leaves indicates, however, that their — 
does not absolutely limit the growth of the shoot. When 
branch produces gemmae at all, they generally occur 0” ean 
of the leaves. A leaf may produce gemmae singly or 17 aie 
In the latter case two or three gemmae are usually found ogee” 
