1912] CURRENT LITERATURE 73 
states that the work does not offer a solution of the perplexing problems or 
attempt a natural history study of the subject. 
The introduction gives a brief résumé of the history of cecidology, of the 
research methods in use, and of the methods used in designating galls. Chap. i 
contains a brief discussion of the general groups of organisms which excite the 
formation of cecidia, including a si 9 the families and genera of insects, with 
the number of known European a by Howarp 
The groups of plants which excite ne formation of cecidia are re given as follows: 
Myxomycetes, Bacteriaceae, Cyanophyaceae, Algae, Fungi, and Phanerogams. 
Examples are given for each group, but no complete lists of genera such as are 
given for the insects. Chap. ii gives a brief discussion of the host plants, 
showing that galls are to be found in all groups from lowest to highest, but are 
most abundant on the flowering plants. The chapter concludes with a list of 
the European and Mediterranean families of angiosperms, with the number of 
known galls (also according to Howarp) on each. This list contains tog 
families, the largest number of galls (gor) being on Fagaceae. In this connec- 
tion it is interesting to note that more than 4000 species of galls occur on 10 
families of dicotyledons. Chap. iii (pp. 102) gives an excellent discussion of 
the morphology of galls. Chap. iv gives a good but not nearly so compre- 
hensive a discussion of the anatomy of galls. Chap. v is a very brief discus- 
sion he es chemistry of galls. 
. vi is a most excellent discussion of the etiology of gall formation, 
and eciee be studied by all botanists and zoologists, especially by those who 
still believe that all insect galls are due to chemicals injected into the host 
plants by the mother insects. Attention is called to the lack of proof to 
substantiate the various theories, the obscure nature of the subject, and the 
failure thus far to produce artificially such galls as are formed by natural 
processes. Theories past and present, with arguments for each, are clearly 
stated, and the susceptibility of the host plant and its parts at various stages 
in its life history are given careful consideration. In this connection the 
a refers to facultative galls, or those in which the organism, although living 
within various parts of the host, can produce galls on certain parts only. In 
this chapter he states that in his opinion an understanding of gall building can 
be obtained only as a result of a comparative study of plant pathology. The 
chapter concludes with a discussion of the correlations between host plants 
and galls, of variations in galls, and of abnormal galls. Chap. vii, on the 
biology of galls, necessarily refers to a great deal of the discussion of the pre- 
ceding chapters. After discussing the fact that some organisms attack and 
cause galls on many species of plants, the author takes up the relationship of 
the life-cycle of the parasite to the life-cycle of the host plant, the problem of 
biological species, gall ecology, distribution, paleontology, development and 
life of the gall, sexual dimorphism, opening of the galls and migration of the 
organisms, uses and injuries, resistance and immunity of the host plants, 
formation and action of poisons, inquilines, parasitic and saprophytic fungi 
