STUDIES OF THE DEVELOPMENT OF PEPEROMIA HISPIDULA 36 1 
as a conducting tissue for the pollen tubes (figs. 78, 100). At least, 
the only structures seen that resembled pollen tubes were growing 
through this tissue. Latticed tracheids, to the number of 10 or 12, 
and with a diameter of from 10 to 25 /z, arise in the tissue of the abaxial 
side of the style. These tracheids form the expanded upper end of the 
slender vascular strand that runs along this side of the fruit (figs. 78, 
100, 107). The position and structure of these tracheids suggests 
that they may serve for water storage, perhaps to prevent premature 
shriveling of the style and stigma. These cells, however, do not reach 
their highest development till some time after pollination. 
We may now take up the details of development of the ovule, with 
its single integument, into the seed with its seed coat. 
The nucellus of the ovule is initiated by the upward stretching of 
the subepidermal cells at the center of the carpellary ring (figs. 53, 54). 
The mound so formed continues its growth until, by the time the 
carpel has closed together above, it forms a cone of about 30 cells in 
vertical section (fig. 56). The growth of the nucellus continues until, 
by the time the egg is differentiated, it is 10 to 15 cells broad and 25 to 
30 cells long (fig. 78). The cells of the peripheral layer are somewhat 
flattened radially, while in the interior of the ovule the short diameter 
of the cells at this stage is the longitudinal one. The group of cells 
above the sac, formed by the division of the parietal cell, consists at 
this stage of 8 or 10 cells thatlshow in a longitudinal section (figs. 81 , 89). 
In ovules that do not give rise to embryo and endosperm, growth of the 
nucellus stops at the stage just indicated. Many ovules that have 
reached this stage and then shrivelled up are found on spikes bearing 
ripe, or nearly ripe fruits. This shriveled condition is probably due to 
the lack of fertilization of the eggs in these ovules. It is true that fruits 
are found in which degeneration set in at an earlier, or at a later stage 
of development, but in by far the larger number of the ovules that 
degenerate, this process seems to begin after the embryo sac is mature 
and ready for fertilization. 
In those seeds where embryo and endosperm are formed, a very 
marked renewal of growth of the nucellus occurs. This growth is due 
only in small part to increase in the number of cells present at the 
beginning of embryo-formation, but chiefly to an increase in the size of 
these cells (figs. 78, 100, 108, iii). The nucellus increases from 125 to 
900 y, in length, and from 90 to 590 ju in diameter. The highly 
vacuolated cells seen in the nucellus in the earlier stage become the 
