the Embryo and Seedling in the Gramineae . 201 
Thus the first node can be distinguished from the entry of the 
scutellum bundle into the axis, although in the younger seedlings both 
occur together. For clearness we begin with one of the older seedlings in 
which the series is fairly complete and the preparations successful. The 
other is less clear, but the main points can be verified in it by comparison 
with the first. 
After remaining distinct from the stele through a few sections, 1 the 
phloem of the upward scutellum trace divides to right and left of the xylem. 
One half goes to form the coleoptile trace P, the other to form F. The 
xylem meanwhile splits into three parts; the lateral branches accompany 
the phloem, while the median elements enter the stele at the gap which 
faces the midrib trace M (cf. II and III, Text-fig. 28, p. 202). They turn 
downwards at once, and do not, therefore, appear in Diagram I of 
Text-fig. 28. 
So much for the behaviour of the scutellum trace on its upward course. 
A more complete view of the first node is gained by following the coleoptile 
and plumular traces downwards. 
A little distance above the first node are eight well-marked plumular 
traces, besides several small ones. Seven of these belong to the first leaf. 
The eighth is the midrib of the second leaf, which divides just above 
the entry of the coleoptile bundles and inserts itself on two lateral traces. 
The coleoptile bundles enter by the gap thus left, which is opposite M, the 
midrib trace from the first leaf. 
The terminations of the coleoptile bundles are sharply bent, one lying 
over the other, but quite distinct. They lie just under the apex of the 
coleoptile, and on the same side of it. A number of spiral tracheides are 
found at the angle of each. Their function is doubtless related to the 
occurrence of the large water-pores which are always found in their 
neighbourhood. Near the first node the bundles are not clearly double in 
transverse section, and they lie a little to one side of the line which bisects 
stele and axis symmetrically (I, Text-fig. 28). Nor do they meet within the 
stele as in Arena, but just outside it (II and III, Text-fig. 28, p. 202). The 
branching at this spot is, however, precisely that of Arena. The ingoing 
branches—a common xylem strand and two distinct phloem groups—enter 
the stele by the gap opposite M, and constitute the bundle x. The 
outgoing branches unite to form the inverted scutellum trace, sc. There is 
also a direct xylem connexion—as explained above—between the scutellum 
trace and x. In this respect again Triticum resembles Arena. 
This vascular symmetry may be described as essentially that of 
an Arena seedling in which the mesocotyl has been reduced in length 
almost to vanishing point. In the two younger Triticum seedlings it 
1 The sections are cut to a uniform thickness of about ioyu. 
