180 
NATURE 
[APRIL 25, 1912 
made, and to point out and direct attention to 
some of the many problems that suggest them- 
selves more or less urgently at each step forward. 
The term “gall” is employed in almost the 
same sense as by Dr. Ross, and the subjects 
treated of by him are also met with in this work; 
but the whole subject is discussed far more thor- 
oughly, and from other points of view, with very 
copious notes and bibliographical references. 
The introduction gives a historical outline of 
the investigation of galls from the earliest records 
onwards. Some of the earlier beliefs as to their 
origin are similar in kind with the strange ex- 
planations of the origin of fungi at the same 
period; and they form a striking contrast to the 
views expressed by Malpighi, the founder of the 
scientific study of galls, in his treatises, ‘De 
gallis” and “De variis plantarum tumoribus et 
excrescentiis.” But for a long period after 
Malpighi, little interest was shown in them except 
by Réaumur, and a catalogue of galls due to 
animals (zoocecidia) published in 1858 included 
only about 300. How rapidly knowledge has 
advanced since then is evident from the catalogue 
by Houard, issued in 1909, enumerating more than 
6000 from Europe and the Mediterranean area of 
Africa and Asia, while numerous records have 
recently appeared on the galls of other 
regions. 
Dr. Kiister divides his book into comprehensive 
chapters devoted to the great divisions of his sub- 
ject, beginning with one on the gall-producing 
animals and plants considered class by class. The 
second consists of a review of the gall-bearing 
plants, also treated systematically. The situations 
of galls on their hosts and their morphology 
receive very full consideration, as do also their 
internal structures and their relations to the 
healthy tissues of the host-plants. Then follows a 
brief account of the chemistry of galls, including 
the physiological processes that go on in them. 
The two last chapters are the most important and 
suggestive of all, the one being devoted to the 
etiology and the other to the biology of galls. 
Under etiology are considered the prerequisites for 
their formation, the varying degrees of ability 
shown by the gall-makers to originate and to 
develop them, general questions as to means 
employed by their makers, the formation of galls 
as affected by absorption, nutrition, and wounds, 
their connection with alterations of correlation in 
the members and tissues of the host, their tend- 
ency to induce permanent variations (very slight, 
as tested by cases where the growth extends 
beyond a gall), abnormal galls, and the informa- 
tion that they yield as to their etiology, and as to 
the effect on their growth of the death of the 
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maker or its early abandonment of the gall. The 
great need of further efforts to produce galls 
experimentally is dwelt on, while the small result 
from the experiments of the past is fully recog- 
nised, and makes still more evident the need to 
observe very carefully the actual course of things 
in the development of galls, both normal and 
abnormal. Many show themselves to result from 
stoppages of advance in complexity, while increase 
goes on in mass of tissues, 
Under the biology are included a number of 
most interesting topics, such as the grade of 
restriction to certain host-plants, alternation of 
generations, with or without alternation of hosts, 
tendency to produce “physiological species” or 
races restricted to certain hosts, though scarcely 
differing morphologically, relative frequency in 
various habitats (e.g. water plants, dry moor and 
mountain floras, deciduous trees, &c.), methods of 
distribution in space, paleontology, relations 
between galls and their makers (duration of life, 
sexual dimorphism of galls, methods of emergence 
of makers), effects of galls on welfare of host, and 
relations to other organisms (feeders on galls, 
inquilines, “ambrosia,” and parasitic fungi, &c.). 
A brief account is given in an appendix of the 
relatively few galls (“thylacia”’) upon the bodies 
of animals. 
Space will not allow of quoting any of the 
remarks on the numerous problems to which the 
reader’s attention is directed as in need of investi- 
gation. For these, as for much else, we must 
refer those interested in galls to the work itself, 
assured that they will find no better or more 
trustworthy guide. Its value will be most fully 
felt by those who have already gained some know- 
ledge of galls in the field. As already stated, it 
does not aim at being a descriptive catalogue. 
Numerous good figures in the text (not always 
correctly referred to, however), and a sufficient 
index add to the value of this excellent work. 
SOIL STRUCTURE AND PLANT GROWTH. 
Boden und Klima auf kleinstem Rawm. Versuch 
einer exakten Behandlung des Standorts auf 
dem Wellenkalk. By Prof. G. Kraus. Pp. 
vit184+Taf. vii. (Jena: Gustav Fischer, 
1911.) Price 8 marks. 
O one can pass from a sand to a chalk forma- 
mit tion without being struck by the very 
sharp changes in vegetation, even where similar 
climatic conditions persist, changes which clearly 
indicate marked or even fundamental differences 
in soil conditions. But so far as we know no one 
has taken the trouble to investigate a particular 
case with anything like the completeness it de- 
