258 BOTANICAL GAZETTE _ {Marcu 
The situation in the oak, however, is somewhat different from 
that outlined for Helianthus and the Compositae generally; for 
in the oak the depressions are xylem segments between the lateral 
compound leaf rays and do not correspond to the leaf trace segment 
itself as in the Compositae. For purposes of elucidation the situa- 
tion presented by the oaks may be briefly reviewed. In Quercus 
the two predominant lateral traces of each foliar organ are related 
to foliar rays which are typically in 5 pairs, corresponding to the 
two-fifths phyllotaxy of the oak. Between these approximated 
pairs of rays there is a ‘‘dipping in”’ of the cylinder as a consequence 
of the retarding influence on growth of the rays in question. 
In some genera of the Compositae we get a situation approxi- 
mating that in the oaks, and as a result contrasting with that 
figured for the sunflower, etc., in fig. 9. In S. graminifolia, for 
instance, the depressions do not correspond to single leaf trace 
segments as is usual in the Compositae, but are in relation to the 
xylem segments between the leaf rays. This situation may be 
noted in fig. 10, a section of S. graminifolia cut in the region of the 
node. The result of the depression of segments between the rays 
is that the stem is roughly divided into 5 parts as in the oak. The 
pith is 5-angled and the median trace comes off opposite an angle 
of the pith precisely as in Quercus. Fig. 11 shows a portion of the 
same more highly magnified, illustrating how striking is the depres- 
sion and how clear the analogy to the oak. Fig. 12, which at first 
sight might easily be taken for a section of an oak twig, is really a 
transverse section of Aster multiflorus, and elucidates this phenom- 
enon even more strikingly. Here there can be no doubt that the 
depressions in the cylinder occur between pairs of rays exactly as 
in Quercus, and do not correspond to single leaf trace segments. 
This topographical condition of the stem is rare in the Compositae, 
although it is occasionally present in Solidago, as for example in 
S. graminifolia, and is extremely common in the genus As/er. 
Summary and conclusion 
Solidago is a genus which occupies a very high place systemati- 
cally and presents both woody and herbaceous types of stem, not 
only in the genus but also in different regions of the axis of the same 
—— The modifications of the stem, especially the transition 
