i35 
the Grain of Wheat (Triticum vulgar e). 
to be arranging themselves into epidermis, cortex, and vascular cylinder. 
Meanwhile the root-cap has been evolving itself, and is now quite clear. 
Rather less than four weeks after pollination the first pair of rootlets 
come into being. These are arranged right and left of the radicle, but 
rather towards the outer side of the embryo, and arise from the very base 
of the hypocotyl, just where it joins the young root. About a week later 
two other rootlets appear above the first pair, with practically the same 
orientation, but a trifle more dorsal. In the course of another week a fifth 
rootlet makes its appearance, lying between the others on the outer side, 
which does not seem to be mentioned by Strasburger. No further root 
development occurs before the embryo enters upon its resting stage in the 
ripe seed. 
Returning to the developing plumule — about three weeks after pollina- 
tion the first leaf is marked out, with a divergence of from the 
cotyledon, with the free tips pointing inwards towards the endosperm. 
This leaf makes far more growth than any of the subsequent ones, so that 
eventually its edges are folded over one another at the tip, the lower 
part forming a tube. Other leaves are soon marked out, so that by the 
time the grain is ripe three or four are in evidence, all with a divergence 
of 
When the radicle and plumule start differentiating the embryo begins 
to shape itself. The tissue lying between these rudiments and the endo- 
sperm gradually spreads itself out into a shield-like mass forming the 
scutellum, which develops a well-marked epithelium towards the endosperm, 
and acts as a sucking organ at the time of germination. This spreads up- 
wards and downwards, as well as laterally, so that at length the young 
plant appears to be borne on the outer face of the shield. 
The initials of the embryonic vascular system are marked out at quite 
an early stage, when the epiblast begins to develop and at the same level 
with it. At first a strand of differentiated cells appears in the hypocotyl, 
which strand turns out into the scutellum, running in it for some way parallel 
to the plumule, and finally disappearing. As time goes on this vascular 
strand gets more clearly marked out, and continues its way through the 
scutellum below the level of the plumule. When first it passes from the 
hypocotyl the cells are somewhat hexagonal in cross-section, but lower down 
they appear elongated, with the long axis at right angles to the ventral edge 
of the scutellum. At length this strand begins to spread out laterally, till 
eventually a fan-like arrangement of conducting cells is formed, which 
continues nearly to the extreme end of the scutellum. 
Soon after the initials of the vascular strand appear in the hypocotyl 
branches pass off from it, one into either side of the cotyledon, but these 
two branches undergo no further division, remaining intact throughout 
development. In due course vascular strands also pass into the first leaf, 
