WATORE 
185 
THURSDAY, APRIL 25; ro912: 
t IN NATURE’S BYWAYS. 
Die Pflanzengallen (Cecidien) Mittel- und Nord- 
europas, ihre Erreger und Biologie und Bestim- 
mungstabellen. By Dr. H. Ross. Pp. ix+ 
350+x plates. 
Price 9 marks. 
Die Gallen der Pflanzen. Ein Lehrbuch fir 
Botaniker und Entomologen. By Prof. E. 
Kiister. Pp. x+437. (Leipzig: S. Hirzel, 
1911.) Price 16 marks, 
MONG the byways that lie in the borderland 
between botany and zoology and appeal to 
the students of both sciences, few, if any, offer 
more attractions than the study of galls. That 
certain organisms can change the modes of action 
of the living substance in some other, and can make 
it produce new structures to benefit themselves, is 
an intervention of a kind to arouse interest. But 
that power is shared by plants and animals of 
widely different types, and so related to others 
that do not possess the power as to indicate that 
it has often been independently acquired. The 
effects produced by some amount to little more 
than sufficient to heal wounds, while at the other 
extreme we find growths unlike any uninjured 
structure of the host; and between these are galls 
of varied forms and structure, each true to its 
type. The wide diffusion of the power to influence | 
the work of the protoplasm seems to point to 
the readiness of that substance to respond to 
certain kinds of stimuli, and to give some warrant 
for the hope that means to regulate its activities 
may be discovered. As yet, however, the attempts 
to produce galls artificially have failed. 
The literature on galls is already very extensive, 
though comparatively recent; but much of it is 
scattered in periodical literature, or forms large 
and costly works. The two before us are among 
the latest contributions to the mass, and though 
comprehensive in treatment are among the less 
expensive books. They treat the subject from 
different points of view. 
“Die Pflanzengailen Mittel- und Nordeuropas,” 
by Dr. Ross, is intended to supply a descriptive 
catalogue of the galls recorded from Central 
Europe and Scandinavia, including those caused 
by plants as well as those of animals. The de- 
scriptions are limited to the briefest possible state- 
ment of the distinctive features, in keys of 
tabular form, of all the galls in each genus. The 
characters have been carefully selected, though 
sometimes too brief; but contractions are freely 
used for the organs of the hosts, and the tables 
have not the clearness of those in Houard’s 
NO. 2217, VOL. 89] 
: | under Quercus, 
(Jena: Gustav Fischer, rg1t.) | 
| maturity. 
“Zoocécidies des Plantes d'Europe.” Somewhat 
above a hundred of the galls caused by animals are 
figured, often with details of structure, on the ten 
plates., All the galls in each genus are treated 
in a single table, the species of the hosts being 
named after the description of each gall, except 
where Cerris receives distinct 
treatment from the other oaks, owing to the multi- 
tude of galls on these trees. For ease of reference 
the genera are arranged alphabetically, but the 
gain is more than balanced by the loss in the 
separation of nearly allied host-plants, and the 
consequent obscuring of the relationships between 
the galls on them. 
The tables are preceded by eighty pages of 
general discussion. The author defines “gall,” in 
the widest sense of the word, as any deviation of 
structure due to growth produced (usually by a 
chemical stimulus) on a plant by an organism 
living parasitically or symbiotically on the plant. 
He treats of the forms and structure of galls, the 
various types of animals and plants that give rise 
to them, the effects on the host-plants, the dis- 
tinction of galls into ‘‘organoid” (which allow 
recognition of the parts of which they are modi- 
fications) and “histoid” (not evidently compar- 
able with parts present in the plant naturally), the 
limitation of the gall-forming response to the 
meristem, the nature of the stimuli employed by 
different gall-makers and of the response to each, 
the formation of ‘“procecidia”? (growths aban- 
doned by the larve very early), and other topics 
of great biological interest, such as the different 
relations to production of galls exhibited within 
the limits of certain species of gall-makers. Some 
of these in alternate generations produce galls of 
different structure on the same host; or they pass 
from one host to another, producing galls on both, 
or on one host but not on the other; or the galls 
may be formed by some individuals (e.g. of certain 
weevils), and occupied by their larve, while 
other larve of the same species may live healthily 
on the same host without a gall being formed. 
The ‘‘ambrosia” galls, in which fungi grow, to 
serve as food for the larve, also find mention. 
Brief directions are given for collecting and pre- 
serving galls, and for rearing the makers to 
Within the limits set, the book will be 
found a helpful and suggestive guide to the deter- 
mination of the galls of Central and North Europe, 
and a good introduction to their study. 
Dr. Kiister’s ‘Die Gallen der Pflanzen ”’ 
not attempt to give an exhaustive list of the galls 
of any one region or country, its aims being to 
afford a comprehensive and trustworthy introduc- 
tion to the study of galls, illustrated by series of 
selected types, to indicate the progress already 
I 
does 
