22 BOTANICAL GAZETTE [JANUARY 
traces. There is little or no cambial activity to be observed in 
these segments. In 6 is shown the upper slender region of the 
same aerial stem. Here the segments corresponding to leaf traces 
contrast with those in the former figure by their outstanding 
character. The absence of cambial activity, however, is to be 
observed as in the foliar segments of the stouter axis. The leaf 
traces are also more numerous than in the other instance, a con- 
dition not at all uncommon in the upper regions of herbaceous 
stems. This phenomenon, for example, is found in the common 
bean, and in many other cases. The depressed segments in the 
slender portion of the stem of Potentilla correspond to the out- 
standing ones in the thicker region nearer the ground. Cambial 
activity is indicated in the depressed portions of the stem separating 
xylem and phloem. The conditions in a woody axis of Clematis 
areshowninc. The depressed segments of the cylinder correspond 
in position to the foliar traces, and are without cambial activity. 
The outstanding arcs, on the other hand, represent the cauline 
bundle system, in which well marked secondary growth is present. 
In d is shown the subterranean perennial stem of Actaea, as an 
example of the essential similarity in organization of terrestrial 
axes to that found in the woody region of the aerial stems of her- 
baceous types. The broad, black, radial bands are the foliar rays. 
In proximity to a node the leaf ray is subtended by a broad radial 
band of storage tissue, and cambial activity, as represented by a line 
separating xylem and phloem, is absent. In the case of traces 
which are remote from their corresponding leaf in the vertical 
plane, cambial activity has been restored and the foliar storage 
parenchyma is divided into two by a woody central isthmus. 
This condition may well be compared with that shown in text 
fig. 1 for Helianthus. The topography of a moderately thick and 
woody node of the aerial stem of Helianthus is shown ine. The 6 
foliar segments of the cylinder are depressed and show the absence 
of distinct cambial activity. The subtending portion of the foliar 
ray is only moderately well developed in this instance to correspond 
to the slight degree of thickening of the stem. In the outstanding 
portions of the cylinder a cambium is present and is conventionally 
represented by heavy lines separating xylem and phloem. In / is 
