114 
associations and related phases of the subject, and all the rest of 
the book deals with the morphologic and physiologic home-econ- 
omy of plant organs and behavior. This, to quote the preface, 
has been done “to develop certain general conceptions that are 
felt to be fundamental." It should be stated, however, that the 
work is not for professional ecologists. 
Within the limits of Professor Cowles' restrictions, it would 
be difficult to imagine a more complete or satisfactory treatment 
of the underlying foundations of ecology. Roots and rhizomes 
are first discussed in their relation to absorptive, anchoring and 
propping functions. Under "root hairs" there is a long discus- 
‘sion of different soil constituents, bog water, salts of various 
kinds, and so forth, and the effect these have on plants, Soil 
exhaustion and its relation to deleterious root excretion is also 
discussed. 
In the long chapter on the ecology of leaves, the first part is 
given over to the discussion of chlorophyll and food manufacture, 
and later the structure and arrangement of chlorenchyma is 
presented. “Тһе Relation of Leaves to tighi, 7 AR e hambers 
and Stomata,” ‘“‘ Protection from E " '"Varia- 
tions in Leaf-form," ''Absorption of Water ded Nor ака 
Solutes of Leaves," ‘“ Leaves as Organs of Secretion and Excre- 
tion," “Leaves as Organs of Accumulation of Water and Food,” 
and ' Miscellaneous Leaf Structures and Relations," are all 
sections of this chapter and will give the reader an idea of the 
scope of the work. 
Lack of space forbids discussion of the subjects presented in 
this chapter, but it may be questioned by some whether the 
sparse undergrowth of hemlock forests is mostly a matter of shade 
(р. 546) ; for is it not related also to the excessive amount of tannic 
acid leached from the trunk and branches during rains, and per- 
haps also in part to toxicity of the decayed leaves of the hemlock? 
In the chapter devoted to stems, a large variety of subjects 
are discussed, such as stems as organs of display, reproductive 
organs, conductive and mechanical tissue, and the accumulation 
of food and water in stems. All the features of ecological signifi- 
cance are treated in detail and with a thoroughness that should 
