FISHER: SEED DEVELOPMENT IN THE GENUS PEPEROMIA 141 
ptimary archesporial cell is differentiated until about the time 
of pollination. About this time the nucellus begins to increase in 
size by the development of perisperm, and the diamond-shaped 
border of the cup increases in height around the developing fruit, 
until at maturity the fruit projects about one third of its length 
(Fic. 17). Sometimes the margin of the cup extends out prac- 
tically as far as the outer end of the ripe fruit. The borders of 
these cups constitute ridges between the flowers, and the tops of 
these ridges and also the peduncle of the spike are rather thickly 
beset with simple, sharp-pointed hairs (Fic. 18). Each of these 
hairs consists of four to eight cells, including the basal cell, arranged 
uniserially, and measures from .15 mm. to .3 mm. in length. 
Among these hairs on the rachis and on the peduncle of the spike, 
and also on the carpels and bracts, there are glandular trichomes 
each consisting of three cells—a basal cell belonging to the epi- 
dermis, a short stalk-cell, and an enlarged terminal cell which 
usually has the shape of a much-flattened oblate spheroid, or door- 
knob (Fic. 18). As Haberlandt (26, pp. 444-455) suggests, these 
trichomes probably serve for the excretion of water (as hyda- 
thodes), or at least for the absorption of water. According to 
Solereder (69), hydathodes of this kind occur not only in Peperomia, 
but also in the related genera Saururus and Piper. 
Large oil-cells are present in the rachis, bracts, and carpels. 
Starch grains are abundant in the rachis and bracts. 
The anthers, as in all other species of Peperomia, are bilocular. 
The masses of archesporium in the stamen, when fully differ- 
entiated, show about twenty-five cells in cross-section. The 
tapetum, which is organized very early, consists of a single layer 
of cells. This layer entirely lines the pollen sac, and thus com- 
pletely surrounds the male sporogenous tissue. At first it is rather 
thin, but the cells increase in size until they are quite large, 
reaching their greatest relative size about the time of the formation 
of the tetrads of microspores (Fic. 19). The walls of the pollen 
Sacs are three cells thick—the epidermis, the endothecium, and 
4 more or less complete and very thin layer inside the endothecium. 
This is exclusive of the tapetum. The microspores are formed 
by the time the primary archesporial cell in the nucellus of the 
Same flower has cut off the parietal cell. The walls of the micro- 
