1918] WHITAKER—ANATOMY OF SOLIDAGO 253 
as-has been shown, in the woody aerial stem of Solidago. It is clear 
that there is a general agreement regarding the part the leaf trace 
plays in relation to the transformation of portions of the woody 
cylinder into a parenchymatous segment. 
Concerning the comparableness of woody types like the oak, 
etc., with those presented by axes characteristically herbaceous, 
however, some doubts have been raised. It has, for instance, been 
maintained by Stnnort and BatLey’ that the herbaceous type does 
not come from the woody through the conversion of secondary 
xylem opposite the leaf strand into storage parenchyma, but, on 
the contrary, that the evolution of herbaceous forms has come 
about through the reduction in amount of secondary wood and 
increase in width of the broad rays. This, together with their 
decrease in radial extent, has resulted in the confining of the storage 
tissue in herbaceous axes to the sides of the leaf trace, with the 
result that parenchyma in no case subtends the trace as in the oak, 
etc. “In practically all families of herbs, the interfascicular 
parenchyma is never subtended by a tiny leaf trace bundle of 
protoxylem, but always abuts directly on the pith tissue between the 
strands of primary wood”? (loc. cit. p. 596). Hence it is assumed 
that the significant conditions in the woody stem in relation to the 
leaf trace are in no way responsible for the origin of the herbaceous 
form. It is further claimed, in substantiation of this hypothesis, 
that the condition outlined for the Betulaceae, etc., while it holds 
for the subterranean parts of the woody axis, does not explain the 
situation in the aerial region of the herbaceous stem where “the 
actual evolutionary development must have taken place (Joc. cit. 
P- 555)- 
The situation in the herbaceous part of Solidago may be de- 
scribed. Fig. 5 represents a slender stem of S. canadensis, which is 
obviously herbaceous. The section was made just below the node 
and shows the three leaf traces at the top. At the bottom and a 
little to the right, the three traces of the next higher node may be 
seen. In the upper part of the figure, even under the compara- 
tively low power of magnification, it can easily be noted that the 
’Srynott, E. W., and Batzey, I. W., Investigations on the phylogeny of the 
angiosperms, IV. The origin and di spersal of herbaceous angiosperms. Ann. 
Botany 28: 547-600. pls. 30, 40. 1914. : 
