1918] WHITAKER—ANATOMY OF SOLIDAGO 251 
There are, as a rule, three traces to each leaf in Solidago, a 
median and two laterals. In some species (for example, S. rigida, 
S. patula, and S. sempervirens) there is a multiplication of traces, 
correlated apparently with the increased size and vigor of the plants 
and especially with the size of their leaves. The species mentioned, 
besides being very large and leafy, are characterized by having 
large, full heads of flowers. 
In studying the modifications of the woody cylinder, the median 
trace need not be especially considered, since conditions here are 
complicated by the presence of the axillary bud. Attention 
accordingly may be directed to the lateral traces, which present a 
simpler situation. The most conservative part of the stem is at the 
node; and conditions at the node, therefore, are the most significant. 
A section cut transversely through the node of the woody axis of 
any of the species of Solidago mentioned shows the leaf traces 
still in the cortex. Following the traces down in serial sections, 
it is to be noted that they enter the woody cylinder a short distance 
below the node and are surrounded on all sides by parenchyma. 
One leaf ttace usually passes into the stele at a higher level than the 
others. Consequently, sections cut at different distances below 
the node show the traces in different topographical relations. For 
a considerable interval downward the trace is surrounded on all 
sides by parenchyma, so that the storage elements are present not 
only on the sides of the trace but confront it externally as well. 
Fig. 1 shows a transverse section of S. canadensis cut far enough 
below the node so that only one of the lateral traces (the one on the 
right which entered the cylinder much lower than the corresponding 
trace on the left) appears surrounded on all sides by parenchyma. 
Figs. 2, 3, and 4 show this situation under higher degrees of magni- 
fication and in the three dimensions respectively. Fig. 2 is a high 
power representation of the transverse section of a lateral leaf trace 
segment of S. canadensis. The foliar strand can be seen lying at the 
bottom of the figure, obviously surrounded by storage parenchyma, 
which both confronts it radially and lies on either side of it. In 
this section it is clear that a portion of the cylinder opposite the 
leaf trace has undergone considerable modification, apparently in 
relation to the photosynthetic activity of the leaf. The cauline 
