484 
Note. 
normal ring, and the interfascicular cambium has developed between the bundles, 
and has consequently taken a somewhat sinuous course in this region. 
In successive sections this sinuous course becomes more pronounced, the inter- 
fascicular cambium taking a radial course and passing along the flanks of the 
sclerenchyma (Fig. i,b). The further removal of the bundle from the normal ring 
leads to closer approximation of the horns of the U-shaped band of cambium, until 
they are separated by no more than two or three intervening cells. 
Apparently the activity of the cambium at these points has been limited to the 
development of xylem. Quite suddenly the cambium is short-circuited both above 
the sclerenchyma and at the level of the normal ring, the middle portion and the inter- 
vening cells differentiating at once into xylem elements (Fig. 1, c). As a result of 
this, a meristematic zone is completed around the pericyclic sclerenchyma of the 
displaced bundle, and at lower levels the activity of this cambium has resulted in the 
formation of concentric layers of both phloem and xylem elements, the latter being 
continuous with the xylem of the normal ring. 
Figs. 1, d, and 2 represent the bundle in its most internal position, and an 
examination of Fig. 2 shows clearly that here the bundle has been too far removed 
from the normal ring to exert any influence on the development of the ordinary inter- 
fascicular cambium. The latter has bridged the gap between the neighbouring 
bundles directly, and a normal development of secondary tissues has resulted. It is 
clear, however, that the activity of the cambium within the bundle has not remained 
uninfluenced by the stimulus of the dividing cells which are giving rise to the inter- 
fascicular cambium, since a formation of meristematic cells along the flanks of the 
sclerenchyma has resulted here also in the establishment of a closed ring of cambium. 
This cambium has been responsible for the laying down of both secondary 
phloem and xylem in such a way as to result in the production of an amphivasal 
concentric bundle, quite isolated from the normal vascular ring. 
KATE BARRATT. 
Imperial College of Science and Technology, 
South Kensington. 
