1918] WHITAKER—ANATOMY OF SOLIDAGO 259 
from one type to the other, therefore, can be studied to good 
advantage in this and other genera of the Compositae. 
In connection with the derivation of the herbaceous type it has 
been shown that the general principles derived from the study of 
the Betulaceae, Fagaceae, Rosaceae, etc., hold equally well for 
this particular genus of the Compositae. Here as there the same 
storage modifications result from the transformation of woody 
tissues surrounding the outgoing leaf traces. No vessels appear 
in the leaf trace segment in the region just below the node, but at a 
lower level in the internode the foliar segment again becomes woody 
with typical vessels and fibers. 
In the slender herbaceous part of the aerial axis the same general 
situation obtains. The traces, however, are relatively well devel- 
oped in proportion to the size of the segment, and the cylinder as 
a whole is thinner. This thinning of the cylinder automatically 
results in the limiting of the storage elements to the flanks of the 
foliar strands in extreme herbs. 
It seems noteworthy that in some species of Solidago, for 
example, in S. sempervirens, but occurring also in other species, there 
is a multiplication of the foliar traces which seems to be definitely 
correlated on the one hand with greater vegetative vigor and on the 
other hand with more numerous and larger heads of flowers. 
Internal phloem in the leaf bundles of the cortex is a general 
feature of the genus and probably of the family. It seemingly 
perpetuates a condition which was once characteristic of the bundles 
of the axis. 
Solidago occasionally resembles the oak anatomically by the 
“dipping in” of woody segments between the leaf rays in contrast 
to depressions in the cylinder corresponding to single leaf trace 
Segments, as in Helianthus and the Compositae generally. The 
depression of the cylinder between leaf rays is the usual situation 
in the genus Aster, which, with certain species of Solidago, are 
exceptions to the general rule for the Compositae. 
In conclusion I wish to thank Dr. E. C. JEFFREY, under whose 
direction this investigation has been carried on, for material, 
valuable advice, and suggestions. 
Harvarp UNIVERSITY 
