400 Hill — The Morphology and Seedling Structure of the 
The exact relation of the endosperm to the perisperm has not as yet 
been determined, but it seems probable that its function may be to produce 
the ferment (? diastase) by means of which the reserves in the perisperm are 
presented in a soluble and easily absorbed form to the developing embryo 1 . 
It is of interest to notice that the relations of the endosperm both to 
the perisperm and to the embryo are of the same nature in the case of the 
normal dicotyledonous embryo of P. pellucida^ — where both the cotyledons 
become green, — as they are in the case of the pseudo-monocotyledonous 
embryo of these geophilous Peperomias, where one of the cotyledons never 
leaves the seed, and is purely an absorptive organ (cf. Text-figs. 1-5, p. 402). 
This fact, coupled with others, to be mentioned later 2 , such as the occurrence 
of stomata, tends to show that this unique method of germination is of 
fairly recent origin in the genus. 
South American Species. 
The fruits of the geophilous species from South America present 
various well-marked external differences as to their general shape, whether 
sessile or stalked, the length of the stigma, and the appearance of the pericarp, 
rough or smooth, &c. ; but when examined in section they appear to fall 
into two groups, which are distinguished from one another by the character 
of the pericarp— whether it forms a broad or narrow belt of cells — and by the 
nature of the glands, which may consist of a group of cells at the bottom 
of a pit (Figs. 18-20, 29, PI. XXIX), or of only a single cell in a slight 
depression (Figs. 3 and 4, PI. XXIX ; Figs. 31 and 41, PI. XXX). 
It will be more convenient to describe the fruits in detail and the 
method of germination of the seeds under the heads of their respective 
species. 
P. PERUVIANA. 
P . peruviana 2, , (Miq.) Dahlst. The fruit 4 is about 1*3 mm. in length 
by *5 mm. in breadth, containing a seed about *6 mm. by -47 mm. (Fig. 3, 
PI. XXIX). The fruit- wall, as seen in section, is composed of 3-4 layers 
of cells, the two or three inner ones being easily crushed and somewhat 
tangentially elongated ; all the cells of the pericarp apparently contain 
chlorophyll. The fruit is bounded externally by a layer of curved and 
tangentially elongated cells with fairly thick brown walls. Interspersed 
amongst these at more or less regular intervals are smaller isodiametric 
cells, slightly sunk below the surface in broad shallow pits (Figs. 3 and 4, 
PI. XXIX). These latter cells have unthickened walls and peculiar 
1 Cf. Johnson, 1. c., p. 333. 2 Vide pp. 403 and 409. 
3 This species, which I collected on the damp hillsides above Guaqui at the south end of 
Lake Titicaca in Bolivia (alt. 13,000 ft.), has been kindly determined for me by Dr. Dahlstedt, 
to whom I sent my specimens. 
4 Vide Dahlst., 1. c., Fig. 9, PI. I. 
