2 BOTANICAL GAZETTE [JANUARY 
separate fibrovascular bundles by a so-called interfascicular 
cambium. The parts of the woody cylinder corresponding to the 
supposed primitive bundles are known in this connection as fas- 
cicular wood, and the sometimes depressed segments which inter- 
vene as interfascicular wood. When the sunken segments occur 
(comparatively rarely, and not widely enough distributed to 
warrant a hypothesis of the origin of the woody stem in general), 
the old view regarded their sunken topography as resulting from 
their later origin through the activity of the belated so-called 
interfascicular cambium. As has been shown by previous reports 
from this laboratory, the depression of segments of the stem in 
trees, vines, and woody herbs is a question of growth mechanics 
and has nothing to do with belated cambial activity. It is inti- 
mately connected, in fact, with the appearance of approximated 
pairs of large rays, resulting from a process of aggregation of the 
smaller rays of the general wood in proximity to the entering leaf 
traces. The large rays undoubtedly make their appearance to 
supply the greater storage necessities, which are a special feature 
of the more efficient representatives of the dicotyledonous Angio- 
sperms. In other words, the large rays so universally characteristic 
of the thicker and more woody regions of herbs, whether aerial or 
terrestrial, are clearly a physiological response to the climatic 
conditions of modern times in cooler latitudes and higher altitudes, 
where storage either in stem or seeds becomes of paramount 
importance. 
Since it obviously can no longer be maintained that the woody 
stem is derived from the apparently simpler herbaceous axis, 
the question naturally arises whether the reverse relation of 
origin exists between the two types. To those possessing 4 
knowledge of the past of the great groups of vascular plants this 
possibility presents no difficulties whatever, since it is certainly 
known that many of the herbaceous living representatives of 
cryptogamic groups have had as ancestors forms of strikingly 
arboreal habit. This situation indeed provoked a long continued 
contest as to whether the treelike Cryptogams of the paleozoic 
periods were not in reality seed plants, as are arboreal types with 
secondary growth at the present day. It has been emphasized 
