300 N. Bancroft. 
in six. Amongst Monocotyledons, the Helobiese are exalbuminous, 
and the embryos of this group possess unilateral symmetry, 
suggesting that syncotyly has taken place along one edge of the 
cotyledonary petioles. Assuming, as Compton does, the primitive¬ 
ness of the Helobieae, it seems as if unilateral symmetry must 
be primitive for Monocotyledons, rather than the Liliaceous 
bilateral symmetry, according to Miss Sargant. The alternative 
is to suppose, with Lotsy (see Diagram IV),' that the Helobiese 
and Liliiflorae are two independent lines from a common stock; the 
first line may have adopted asymmetrical syncotyly, having origin¬ 
ated in an ancestor with exalbuminous seeds, while the second, 
descending from an albuminous type, became symmetrically 
syncotylous. 
2. Heterocotyly. Heterocotyly, according to Lotsy (42, 
p. 624), may be of different kinds. Firstly, there may be a division 
of labour between the cotyledons, one remaining in the seed and 
becoming a suctorial organ, and the other escaping and forming the 
first assimilatory organ. 
This view is well illustrated by certain geophilous species of 
Peperomia described by A. W. Hill in 1906 (32; figs. 1-9, p. 420). In 
this genus a series may be traced from species which are truly 
dicotyledonous—for example, Peperomia pellucida —to species in 
which there is a monocotyledonous club-shaped absorbing organ, 
from which all traceof its original leaf-likecharacter has disappeared, 
as in Peperomia parviflora. Peperomia peruviana is an intermediate 
stage, both cotyledons having a distinctly leaf-like form, but one 
remaining within the seed and forming an absorbing organ, the 
other becoming the first aerial assimilating organ. 
According to Hill, the cotyledon of some of the Araceae and 
Tamils communis is closely comparable with the absorbing cotyledon 
in Peperomia, and their first leaf with the aerial organ of that form. 
He believes that monocotyly arose by division of labour between 
the cotyledons on account of adaptation to a geophilous habit, and 
the consequent necessity for an efficient absorbing organ within the 
seed. Its efficiency would be helped by the removal of all other 
embryonic structures from the seed as soon as possible after 
germination ; consequently the rudimentary assimilating cotyledon, 
the plumule and radicle are carried down into the ground. Thus 
in course of time, one cotyledon may have become developed so as 
“ to form a pseudo-terminal absorbent organ (Text-fig. 7, p. 420), 
