722 
DUNCAN S. JOHNSON 
topographically, of three microsporangia, though according to 
Bower's definition it would be a single sporangium. 
The outcome of this consideration of the facts stated must be 
to emphasize the lack of any definiteness in our conception of the 
sporangium as an individual organ, a lack which has been most 
clearly indicated, perhaps, in recent literature, by Bower's defini- 
tion, above quoted. 
The suppression or reduction in development of microsporangia 
may, as we have seen, be carried so far that the stamen is left 
quite sterile (figs. 32, 34). In still other cases, as in some female 
flowers, the stamen is apparently not represented by any struc- 
ture, not even a staminodium. Even where pollen is formed it 
appears sometimes not to be functional, if one may judge from 
the withered microspores seen in flowers where other tissues seem 
well fixed. 
The question of the greatest importance in connection with the 
present study is that concerning the factors which change the 
course of development of certain stamens in such a way that the 
normally fertile portions remain sterile, or, in other cases, the 
cells of normally sterile regions become fertile. This question 
will be considered after we have noted the development of car- 
pels and ovules. 
The wall of the ovary in Piper betel arises as a ring-like but lob ed 
outgrowth, at a point just above the subtending bract of the 
flower. It is therefore between the two stamens, in the case of 
the hermaphrodite flower (figs. 2, 4, 13, 33, 44). Soon after this 
circular wall has closed in above the ovarian cavity, the ovule 
appears as a slight mound at the bottom of this cavity (fig. 2). 
The lobes of the ovarian wall elongate considerably as growth pro- 
ceeds, and give rise in the mature flower to the three- or four- 
lobed stigma (figs. 13, 25, 35, 36, 37) . The lobes of the ripe stigma 
are somewhat pointed and papillate (fig. 44), but after pollina- 
tion, they thicken at the base and shrivel at the point, till in the 
mature fruit nothing but three or four blunt warty tubercles 
remain (figs. 65, 66). The number of these lobes usually present 
at the tip of the carpellary wall, and the presence of three par- 
tial diAdsions in this wall, some distance below the tip, indicates 
