Mottier. — The Embryology of some Anomalous Dicotyledons . 45 1 
cross-sections taken at right angles to the longitudinal axis of the embryo, 
a series of outlines of similar sections of embryos in different stages of 
development will be given. These sections not only show the shape of the 
embryo, but also that part involved in the formation of the cotyledons, and 
the changes taking place in their early formation. Fig. 17, a to/, includes 
the whole embryo, with the exception of the first two cells of the suspensor 
and fragments of some cells at the distal end. The sections of this embryo 
were cut 7*5 microns in thickness, a to k represent alternate sections; 
/ to / successive sections. Sections m to p of this figure show unmistakably 
that the formation of the cotyledonary primordium involves almost the 
entire end of the pear-shaped embryo, and that this end grows out into 
a thick crescentic mound or ridge. The entire embryo at this stage 
(Fig. 6) is a pear-shaped object with a curved indentation on one side at 
the broad end, which extends quite, or nearly, to the centre. Fig. 6 was 
carefully constructed from the series of sections shown in Fig. 17. The 
anatomical details of the embryo at a slightly later stage, as seen in 
a transverse section passing through the base of the cotyledons and 
including the tip of the stem, are shown in Fig. 14. At this stage, and 
even earlier, the formation of the plerome- strands (//, Fig^iq) in each 
cotyledon is very evident, and the central position of the apex of the stem 
(. st , Fig. 14) is clearly indicated. With further development of the embryo, 
growth becomes localized in the cotyledonary primordium in such a way 
that a cleft is formed exactly opposite the original sinus, as indicated in 
Fig. 19, a-k. In this manner the two opposite and symmetrical halves 
of the cotyledonary primordium develop into the two cotyledons. At the 
stage of development represented in Fig. 19, we have an embryo with two 
cotyledons possessing a common base, and in which one of the sinuses 
between the cotyledons is twice as deep as the other. A median longitudinal 
section of an embryo similar to that of Fig. 19, taken at right angles to the 
flat surface of the cotyledons, is shown in Fig. 7. In this and similar 
sections there is nothing to indicate definitely that the two cotyledons have 
arisen from a common primordium, for the figure seems to coincide in 
every respect with that from a typical dicotyledonous embryo. At this 
stage (Fig. 7), it will be seen that the plerome- strands in the cotyledons 
and hypocotyl are becoming well defined. The suspensor is short, being 
one or two cells wide at the free end, but more massive at its juncture with 
the body of the embryo. As the embryo continues its development in the 
seed, the inequality in the depth of the sinuses, as shown in Fig. 19, is 
maintained in some individuals until a later stage, but growth is such that 
this difference in depth is somewhat equalized when the seed is mature. 
However, in the ripe seed, embryos are frequently found in which the 
sinuses are of unequal depth, and we have then cases of anomaly of 
a pronounced character (Fig. 8). This figure was constructed in the same 
