200 Sargant and Arber .— The Comparative Morphology of 
In such specimens the plumular traces, the stele of the primary root, and the 
main scutellum bundle are all cut transversely in the same series of sections. 
In many seedlings, however, the base of the plumule makes a considerable 
angle with the scutellum and primary root, or is almost perpendicular 
to them. Such specimens are useless for interpretation of the nodal 
structure. We are fortunate, however, in having secured series of sections 
through four straight seedlings, two in which the plumule is still enclosed in 
the coleoptile, and two rather older—the first leaf having pushed its way 
Text-figs. 25-7. Triticum milgare, Vill. 25. Outline of very young seedling, life-size. 26. Out¬ 
line of older seedling, life-size. 27. Outline of still older seedling, life-size. 
out. The following description of insertion and nodal structure is founded 
on those four seedlings only. 
In the two younger seedlings the main bundle of the scutellum runs 
straight into the stele on entering the axis. But in the two older specimens 
it turns upwards, and is parallel to the stele for a short distance before 
entering it. Thus a few sections show the inverted scutellum trace side by 
side with the stele, just as in A vena. A mesocotyl can hardly be said 
to exist, for the vertical distance during which the inverted scutellum trace 
is distinct from the stele is very small. In our best specimen it does not 
exceed 0-05 mm. The structure of the node is certainly clearer for this 
brief interval, however, and more readily comparable with that of Arena. 
