195 
the Embryo and Seedling in the Grammeae. 
independence completely throughout the nodal region. In the two other 
seedlings from which we possess complete series of sections through the 
first node, the phloem groups of each coleoptile trace seem prolonged into 
two groups in the mesocotyl, and to remain fairly distinct during the 
complications of the first node. 
Thus in Zea^ as in Sorghum , the scutellum trace can be followed from 
its entry into the stele upwards to the first node, where it divides. Each 
branch forms half one of the coleoptile traces. The other half is prolonged 
downwards into the stele of the mesocotyl, and is found throughout its 
course side by side with the upward scutellum trace. Thus from first node 
to scutellum insertion, a transverse section shows the double scutellum 
trace, with a trace derived from the coleoptile on either side. Below the 
scutellum insertion the main axis becomes the primary root. The transition 
from the stem structure of the mesocotyl to the characteristic structure 
of the primary root is masked by a very complicated insertion plate. 
When the stele emerges from this region it is completely root-like. 
Coix L aeryma-Jobi, L. Of the four seedlings cut, only one is so young 
that the first leaf is still enclosed in the coleoptile (Text-fig. 22, p. 196). In 
the others, two leaves have unfolded. The first (Zj) is only sheathing ; 
the second (L 2 ) is a foliage leaf (Text-fig. 23, p. 196). 
The scutellum is fleshy and wrapped round the axis. Its apparent 
insertion is prolonged for some distance, but the single massive bundle 
enters the axis almost at once, and often joins the mesocotylar stele above 
the level at which its structure becomes obscured by the entrance of steles 
from the insertion roots. In such cases the xylem and phloem of the 
scutellum trace can be followed up the main stele with some accuracy. 
From apex to insertion the scutellum bundle branches freely, and 
even as it enters the axis branches are still given off to supply the lower 
part of the organ. The main trunk becomes amphivasal from constant 
insertion of branch bundles, and is still amphivasal at its junction with the 
axis. The external xylem on its dorsal and lateral faces enters the down¬ 
ward branches for the most part, and the main bundle carries nothing but 
its compact mass of ventral xylem into the mesocotyl. 
The phloem of the scutellum bundle is sometimes clearly double and 
always massive. Its outline in transverse section is kidney-shaped, at any 
rate near the insertion ; the concavity occupied by ventral xylem. On 
entering the axis it approaches the stele very gradually, so that a section 
just above their junction may cut both scutellum trace and stele almost 
transversely. 
In such a section the ventral xylem group of the scutellum trace 
is easily recognized on its upward course in the stele (px x in Text-fig. 24, 
p. 197). The phloem groups on either hand (pk x and pUi) represent those of 
O 2 
