392 
DUNCAN S. JOHNSON 
instead of the more primitive number, 4, that is found in most angios- 
perms. The ovary is of a single carpel, with no indication of the tricar- 
pellate condition of which there seem to be clear traces in the develop- 
ment of its ally Piper. 
3. The nucleus of the definitive archesporial cell has a thin, darkly 
staining concave disk lying just within its wall. This cell divides, 
with a characteristic synapsis and reduction in its nucleus, to 4 tetra- 
hedral megaspores. The delicate walls of these megaspores soon dis- 
appear, leaving their 4 nuclei in a single, continuous protoplast. This 
globular tetrad of spores is probably a recent innovation in the develop- 
ment of this genus. It is perhaps a modification of the linear series of 
spores, characteristic of Piper and of most other angiosperms, that is 
related in some way to the globular form of the archesporial cell and 
sac of Peperomia. There is surely no adequate evidence that this 
tetrad arrangement has come down directly from a primitive ancestral 
form. 
4. The four megaspore nuclei divide in the single protoplast to 
form one compound, i6-nucleate gametophyte, or embryo sac, con- 
sisting of an egg and a synergid, which are both from one megaspore, 
and of a huge endosperm nucleus formed by the fusion of the remaining 
14 nuclei. This compound embryo sac has no ancestral fore-runner 
among gymnosperms or pteridophytes and is therefore regarded as a 
recently specialized type. It probably has arisen independently in 
that genus, for physiological reasons that have not yet been made 
clear. Quite rarely peripheral cells are formed, but only one or two, 
instead of the half dozen, characteristic of the other, probably more 
primitive, Peperomias that have been studied. 
5. A cell wall immediately succeeds each division of the large 
endosperm nucleus and an endosperm is formed of 100 or more cells, 
containing some oil globules but no starch in the mature seed. This 
type of endosperm formation, which is found in no simpler plants 
nearer than the Marsiliaceae, cannot be regarded as primitive. Starch 
for the nutrition of the embryo is stored in the perisperm. This is 
probably not a primitive feature in angiosperms, since it does not occur 
in either gymnosperms or pteridophytes and is not known in any un- 
doubtedly primitive angiosperm. 
6. At germination the small, globular embryo is enclosed and 
nourished by the swelling endosperm until the primary organs of the 
former are organized. The tips of the cotyledons remain enclosed in 
