1904] SARGANT: EVOLUTION OF MONOCOTYLEDONS 329 
This view is strengthened by what we know of the development 
of the embryo among pseudo-monocotyledons. Scattered here 
and there among normal dicotyledons are species, or small 
groups of species, which on germination show a single seed leaf. 
There is no doubt whatever as to the affinities of these forms. 
We can safely assume that at some geologically recent period 
the common ancestor from which sprang all the species in the 
genus Corydalis, for instance, must have possesséd two distinct 
cotyledons. Most species of Corydalis still possess two, but C. 
cava and a few allied forms have but one. There can be no 
doubt here that the species with a single seed leaf are derived 
from an ancestor with two. It would seem that the early history 
of the embryo ought to throw light on the way in which this took 
place. In such a form as Corydalis cava we should expect to see 
the bifurcation begin in the very young embryo, and that the two 
members thus indicated would later be reduced to one, either by 
the abortion of one of them or by the union of both. 
Hegelmaier® described the formation of the embryo in several 
pseudo-monocotyledons in 1878. He worked out every detail 
in three species, beginning with the fertilized ovum and ending 
with the ripe seed. In each case he examined for comparison 
the embryos of closely allied species in which both cotyledons 
Were present. His work has been completed by that of Sterckx’? 
and Schmid,® who have traced the development of the embryo in 
those three species through its long period of maturation within 
the ripe seed down to the epoch of its germination. 
In Ranunculus Ficaria, Corydalis cava, and Carum Bulbocastanum 
the history of the embryo from fertilization to germination is now 
complete. In all three species the cotyledon is single from the 
first. No bifurcation appears at any stage, though the cotyledon 
of Ranunculus Ficaria soon becomes—and remains—slightly 
two-lobed. The plumule is formed in a deep cleft which marks 
Stuttgart, 
: ° HEGELMarrR, F., Vergleich. Unters. iiber Entwick. dicot. Keime. 
1878. 
7 STERCKX, R., Recherches anat. sur l’embryon et 
culacées. Mém. Soc. Roy. Sci. Li¢ge III. 2:—. 1899 
®Scumip, Beitr. zur Embryo-Entwick. einiger Dicotylen. 
1902. 
les plantules . . . . des Renon- 
Bot. Zeit... 60: 207. 
