1 1 6 Sargant and Robertson. — The Anatomy of the 
Finally, each growing-point has its own sheath : the coleoptile encloses 
the plumule (cl. in Fig. i), and the coleorhiza the radicle (cr. in Figs. 1-6). 
The insertion of these sheaths on the axis, and of the axis on the scutellum, 
is shown in Fig. i. 
The coleoptile is sharply pointed and stiffened on either side by 
a vascular bundle. It protects the young stem until the whole shoot is 
clear of the soil, and is sometimes over an inch long. The rolled-up leaves 
of the stem-bud finally break through the coleoptile, near the apex but 
a little to one side of it. 
In Fig. 2 the root-sheath or coleorhiza is seen emerging from the 
covering of the grain. It never attains the length of the stem-sheath, and 
is soon penetrated by the primary root. Though less differentiated than 
the coleoptile it is a true sheath, and not a mere mass of tissue within 
which the radicle is formed endogenously. 
The primary root (R, Figs, i and 6 , PL V) grows vigorously when 
once started, and continues for many weeks to be the chief root-organ of 
the seedling. Two cauline roots appear very early between the scutellum 
and the young stem (r' r' in Figs. 6, 7, 8, 9). They are symmetrically 
placed on either side of a median section through the whole embryo, such 
as that shown in Fig. 1 on Plate V, and accordingly their insertion only 
(/) is shown in that figure. They grow upwards, appearing over the top 
of the scutellum a few days after germination (Fig. 9). These twin 
roots break through the tissues of the young stem just at the base of 
the cleft dividing it from the upper part of the scutellum (Fig.. 6). 
They press against the inner face of the scutellum in growing upwards, 
and the first effect of their growth is to widen this cleft by pressing the 
stem-bud outwards (Figs. 5 and 6). This mechanism no doubt aids the 
ascending axis to get clear of the seed, and it is possible that the cleft 
itself — which in the damp soil is sure to be filled with water-may be 
useful as a reservoir, tapped for a few days by the twin roots as they 
lengthen. 
The twin roots curve sharply downwards so soon as they are clear 
of the seed and enter the soil, where, like other cauline roots, they serve 
as auxiliaries to the main root. When growing Maize in pots in a green- 
house, we often observed the seed with the lengthening stem-bud attached 
to be raised above the surface of the soil on a tripod formed of the primary 
root and the twin cauline roots. This recalls the stilt-roots of Pandanus 1 . 
But we do not know whether the habit is characteristic of Maize 
germinating under natural conditions. 
The shape and position of the scutellum are shown in Figs. 1, 3, 4, 
5 and 6 on PL V (cf. also Figs. 7-10). It is in contact with the endo- 
sperm over almost the whole of its dorsal surface. It supplies food to other 
1 Kerner and Oliver, i The Natural History of Plants,’ vol. i, p. 756. 
