Mottier . — The Embryology of some Anomalous Dicotyledons. 453 
insensibly into the remainder of the embryo, unless the three cells mentioned 
above are to be regarded only as the suspensor. In Fig. 20, the embryo 
shows a slight depression in the centre of the broad, flattened end. The 
part surrounding the depressed centre now grows faster to form the 
primordium of the cotyledons. Serial cross-sections of a slightly older 
stage (Fig. 21) show beyond a doubt that the thick, crescentic ridge-like 
primordium of the cotyledons obtains here as in Actea. Fig. 21, tf, which 
is the first successive section (7*5 microns in thickness) below this primor- 
dium, shows that the embryo is somewhat flattened at right angles to the 
plane of the cotyledons, a phenomenon of usual occurrence in the embryos 
of the several species with which we are dealing. Later the embryo 
becomes more cylindrical. In c, Fig. 21, it will be seen that the apex of 
the stem is recognized as a very small rounded protuberance exactly at the 
centre of the space enclosed by the cotyledonary primordium. Fig. 22, a-d , 
is a series similar to Fig. 21, taken from an embryo only a little further 
developed. Section d of this figure includes the distal end of the embryo, 
and shows what would be seen by looking directly upon this end. The 
bifurcation of the primordium opposite the primary sinus is just perceptible 
in the section, being indicated in the figure by dotted lines. The apex of 
the stem can also be recognized as a small rounded elevation. A median 
longitudinal section, at right angles to the plane of the cotyledons, is shown 
in Fig. 23. It is apparent now that the growth of the embryo of Sanguinaria 
canadensis , immediately following the pear-shaped stage, results in a very 
marked increase in the width of the distal end with scarcely any increase 
in length. The suspensor is comparatively very short. With the final 
development of the embryo, culminating in the ripe seed, the same pro- 
portion of increase in size is maintained (Fig. 24, a-h ). a to c of this figure 
represent consecutive sections, beginning at the base of the cotyledonary 
primordium, while d to h are alternate sections. It is clear from this 
series, which was made from an embryo in the ripe seed, that the common 
base of the two cotyledons has undergone intercalary growth, the result of 
which is that the primary sinus is deeper (22 microns) than the other. 
The apex of the stem, although central, extends slightly upward, as if 
adnate to that part of the cotyledonary primordium directly opposite the 
primary sinus. The cotyledons are crescentic in cross-section at the base, 
but become gradually more flattened near their tips. Fig. 25 has been 
constructed from all the sections of the embryo, represented only in part 
in Fig. 24, and it shows the condition of the embryo in the ripe seed. We 
have therefore in the mature seed of Sanguinaria an embryo broader than 
long, in which the difference in depth of the two sinuses of the short and 
widely divergent cotyledons is only slight. The suspensor is short, 
consisting of only a few cells. The apex of the stem is recognizable as 
a small, rounded protuberance at the centre of the area surrounded by the 
