20 
Review. 
root making its way through the cortex of the stem was that some 
of the cortical cells of the latter, in front of the root, resembled 
secretory cells in the nature of their protoplasm and nuclei. This 
character and the appearance of the adjacent cells suggested 
partial auto-digestion of the cortex preceding solution and absorp¬ 
tion by the “ poche digestive.” 
In the description of the root-apex, the author quotes Treub 
as having found in palm-roots a well-defined pleromic group, 
covered by an initial layer common to calyptrogen, dermatogen 
and periblem. His own observations referring to the apices of 
large roots of Areca sp. and Kentia sp. apparently revealed the 
presence of “a common initial group similar to that described by 
De Bary for Vanda .”. Considering the statements of Treub 
and others (as to the presence of more than one group of initials) 
and the difficulty of determining the median section when the 
apical meristem is bulky, it is to be regretted that the author did 
not examine smaller apices (including those of rootlets) for com¬ 
parison with the large ones, which he chose for investigation. 
As regards the vascular system, the special peculiarity of the 
adventitious roots of palms, stated in general terms, is that in their 
basal region they show several partial vascular cylinders instead of 
the single one, which is found nearer their apices. Numerous 
separate bundles form the attachment of the root-cylinder to the 
bundles of the stem ; the bundles of attachment, if traced outwards, 
may be said to fuse together to form arcs or cylinders of vascular 
tissue, and these in turn fuse in various ways so as to produce 
ultimately the closed ring of the normal root. These fusions are 
generally accomplished in the basal region of the root, which is 
immersed in the cortex of the stem, but in certain cases the fusion 
is delayed, so that separate strands forming an incomplete cylinder 
are found in the free part of the root for a considerable distance. 
The root, external to the cortex of the stem, often contains a pith, 
in which there may be one or more free vascular strands. These 
are continuous proximally with vascular arcs or bundles of 
connection. 
The author (p. 429) appears to attach importance to the' 
fact that separate procambial strands in the apex are the precursors 
of the separate vascular strands of the root-base, and that the 
successive changes from vascular strands to a lobed cylinder, and 
finally to the normal cylinder of the root, are due to progressive 
changes in the procambial tissue of the meristematic apex. As far 
