236 The Botanical Gazette. [June, 
from the examples which all have -noticed of vines twining 
about trees or of ligatures left unintentionally for years about 
trees. Since the elements of the bundle of woody plants nor- 
mally live but a few years, it follows that beneath a ligature, 
such as those just mentioned, which has prevented radial ex- 
tension in a tree for many years, the elements of the bundles 
must live longer than normally, otherwise we should have the 
whole zone dying and the stem above the ligature also dying. 
VI. If during primary or early secondary extension in @ 
dicotyledonous stem, with pith of not great resistance, radial 
growth be prevented by external mechanical means, there will 
Sollow a displacement of the fascicular zone toward the axis of 
the stem, caused principally by the extension of the cortical 
cells. Later, however, the cortex will be crowded back by the 
growth of the fascicular zone. 
VII. When an external pressure is great enough to prevent 
the derivatives of the cambium from attaining their normal 
stze, the cambium will still continue to form new cells. This 
ts an expression of the fact that the power of extension im the 
cambium ts greater than that in derivatives of the cambium 
some distance removed from tt. — 
University of Michigan, Ann Arbor. 
