115 
set an ideal for all users of the book. On page 708 the statement 
that “alligator” bark is caused by the division of the bark into 
blocks of somewhat equidistant transverse and longitudinal 
furrows may excite some comment. It is quite certain that the 
peculiar bark feature there described may be characterized by 
such furrows, but hardly caused by them. This touches closely 
the question of anthropomorphism, which while specifically 
disavowed by Professor Cowles, is nevertheless a common form 
of expression throughout the book. Without a skillfully devised 
and obviously clumsy form of expression, it is almost impossible 
to write of the ecological factors of plant economy without 
drifting into a more or less anthropomorphic style. 
It may be truthfully stated that no recent text book has 
given such a thoroughly satisfactory treatment of saprophytism 
and symbiosis in so far as these subjects deal with ecological 
problems, as the one at hand. The principles underlying the 
functional activity of plants wholly autophytic and those “whose 
existence depends upon antecedent or coexistent organic forms," 
must be recognized by those who study the habits and environ- 
mental necessities of plants. Furthermore, the practical bear- 
ing of the subject is limitless, as the cultivation of crops and of 
thousands of individual plants can only be successfully accom- 
plished by a thorough understanding of this perplexing relation 
of one plant upon another, and by the application of these prin- 
ciples to horticultural and agricultural practice. In the sec- 
tion dealing with parasitism there is a discussion of grafting 
and the influence of stock and scion upon each other. The 
formation of galls, nitrogen-fixing bacteria, and the mycorhizal 
problem, together with the nature of lichen symbiosis, are also 
fully discussed 
More than one hundred pages are given over to reproduction 
and dispersal, both in the so-called seedless plants and in the 
Spermatophyta. Among the latter, particular attention is drawn 
to the modes of pollination by wind and water, and a long dis- 
cussion of insect pollination deals with this important branch 
of ecology. This, almost exclusively, deals with the intricate 
methods of pollination in various types of flowers and by various 
