36o 
DUNCAN S. JOHNSON 
with the proper bundle of the stalk until the base of the stalk is nearly 
reached (figs. lOO, io8). The central vascular strand consists of but 
3 or 4 xylem elements, and perhaps a few phloem elements. These 
are embedded in a mass of parenchyma. The central bundle ends 
above, with a considerable number of bent and spiral tracheids, just 
below the thickened cells of the chalaza (fig. io8). The walls of 
these latter cells begin to thicken before the fruit has attained its 
mature size. It seems evident that food material brought up by the 
bundle and the parenchyma of the stalk must be able to pass through 
these partially thickened cells of the chalaza, for the walls of the in- 
tegument, the only other possible path to the ovule from without, are 
at this time, still more greatly thickened. The stalk, as has been 
stated above, finally ruptures at the constricted portion of the base, 
and thus sets the ripe fruit free. At this constriction the stalk is 
abruptly narrowed to half the diameter, it has immediately above, 
and the epidermal cells are very thin-walled. Both these features of 
the structure make the break easier, and strictly localize it (figs, icq, 
107, 108). 
The style and stigma are developed by the continued growth of 
the upper margin of the carpellary ring, after the latter has closed 
together above the ovule to form the distinct stylar canal (figs. 56, 57). 
The stigma is formed solely from the abaxial and longer lip of this 
upgrowing carpel (figs. 78, 100). It consists, when ready for pollina- 
tion, of a knob or rounded end made up of parenchyma, and covered 
by a layer of papilla-tipped columnar cells. These latter have large 
nuclei and dense cytoplasts, and form the surface for the attachment 
of pollen grains (fig. 78). With the initiation of the endosperm the 
mature stigma shrivels and remains on the ripe fruit as a cap of black 
cells at the end of the style (fig. 107). No germinated pollen grains 
were detected on the stigma. 
The style of this plant which is remarkably long for a Peperomia, 
is marked off from the stigma by a definite constriction (fig. 78). 
From this point down to the shoulder of the fruit the style is 180 to 
200 fi long and about 150 /x in diameter. The ordinary epidermal 
cells are interspersed with oil cells and hydathodes, but no bristles 
(figs. 100, 107, 108). Internally the style consists of more or less 
elongated cells, which are at first much alike (fig. 57). Later longi- 
tudinal walls, in the neighborhood of the stylar canal, give rise there 
to a small-celled tissue, with dense protoplasts, which evidently serves 
