STUDIES OF THE DEVELOPMENT OF PEPEROMIA HISPIDULA 359 
The glandular hairs, or hydathodes, as they probably are in func- 
tion, occur only on the stalk, style, and adjoining base and tip of the 
ovary (figs. 78, 100, 108). The structure of these hydathodes is the 
same as that of those occurring on the leaf. With the ripening of the 
fruit the hydathodes may shrivel somewhat and turn brown, and the 
outer cells may sometimes drop off (fig. 108). 
The most highly specialized of the cells of the surface of the fruit 
are the tapering, unicellular bristles. These project radially from all 
sides of the swollen fertile portion of the ovary, and are found nowhere 
else on the plant (fig. 107). Each bristle is initiated by the protub- 
erance of one of the larger surface cells of the carpel, which occurs at 
about the time the endosperm nucleus is being formed by fusion 
(fig. loi). The cell continues to elongate until it attains a long coni- 
cal form with a diameter of 8 or 10 yu at the base, and a length of 300 or 
400 /X. The mature bristle has from 2 to 6 longitudinal ribs along 
the inner surface of its wall, each of which may become 2 or 3 /x in 
thickness and 5/1 wide (figs. 108, 109). At the base of the bristle 
these ribs run down to the inner wall of the epidermal cells, and there 
may be bent outward, thus bracing the bristle more effectually (fig. 
108). These bristles remain intact, stiff and rigid, on all the mature 
fruits seen. It is therefore, possible that they may be effective in keep- 
ing snails and small insects ofT the fruits, but no conclusive evidence 
has been obtained on this point. It is of interest to note the relatively 
late appearance of these bristles, as compared with that of the multi- 
cellular hairs of the leaf, which appear while the latter is still very 
young. 
Besides the middle, fertile portion of the ovary, with which we 
have thus far been concerned, there are certain interesting structures 
to be noted in the basal stalk and the terminal style and stigma. 
The stalk of the ovary and of the fruit, though not as long as in species 
like P. obtusifolia, is still quite distinct (figs. 78, 100, 107). It has a 
length, from the chalaza to its insertion on the axis, of about half a 
millimeter. Its diameter is about .2 of a millimeter. The epidermis 
of the stalk is like that of the body of the fruit, except that bristles are 
absent and hydathodes are abundant. The most interesting feature 
of the internal structure of the stalk is the vascular tissue. For two 
thirds the way downward from the chalaza there are two distinct 
groups of these cells. One group is central or axial ; the other, coming 
down from the abaxial side of the body of the carpel, does not fuse 
