1918] WHITAKER—ANATOMY OF SOLIDAGO 255 
herbaceous condition in a dicotyledonous stem. In A the condition 
presented by figs. 2, 3, 4, and 6 is illustrated. The departing leaf 
traces in the region of the node, especially as they bend outward 
through the cylinder, are both flanked and subtended by storage 
parenchyma, a situation shown diagrammatically in black. B 
illustrates the topography of the herbaceous region of the stem in 
the Compositae, where, by reason of the greater relative importance 
of the leaf trace, its radial diameter nearly equals that of the ordi- 
nary xylem segments of the cylinder. As a consequence, the con- 
fronting parenchyma of A is conspicuously absent and the storage 
rh P+ 
SPALL Leer. 
yO OMe 
‘ef 
+ 
Fic. r 
tissue, as a necessary geometrical result, is confined to the flanks 
of the narrower segments representing the foliar strands. This 
exaggeration of the leaf trace in the herbaceous type is probably 
in response to the greater relative size and importance of the leaves. 
That the situation outlined in B obviously results from the thinning 
of the cylinder, with the consequent confining of the storage tissue 
exclusively to the sides of the trace, will be evident by referring to 
A and supposing the woody cylinder here to be considerably reduced 
in thickness. This hypothetical thinning of the cylinder is repre- 
sented by a broken line drawn through the stele just outside the 
leaf traces. A comparison of the portion of the cylinder thus 
limited in A with the herbaceous type represented in B shows that 
the conditions inside the broken line are substantially the same as 
