202 Sargant and Arber .— The Comparative Morphology of 
has disappeared altogether, and the insertion of the scutellum bundle takes 
place aTthe first node. 
The process may be shortly described from above downwards. The 
coleoptile bundles meet outside the stele, but the external branches go to 
form the main bundle of the scutellum itself, not merely an inverted trace. 
Text-fig. 28. Triticum vulgare, Vill. Four diagrams of axis in transverse section. I. Base of 
first internode ; bud in axil of coleoptile. II. Top of first node ; rp., rp ., root-plates. III. Middle 
of first node. y IV. Base of first node; sc'., scutellum trace. 
The internal branches form a compact bundle which is prolonged down¬ 
wards below insertion level, and can be recognized until the stele becomes 
root-like. There is a direct connexion by xylem arch between this trace 
and the scutellum bundle. In both the seedlings we are now considering 
the cauline roots are rudimentary, but the root-plates are present below the 
first node, and effectually mask the transition to root-structure. In the 
