510 The Botanical Gazette. [December, 
ceived in a very different spirit from the first part, however. It is not 
separated into experiments, but it is a short treatise upon chemical 
manipulation. In the opinion of the reviewer it is not a work upon 
chemical physiology, but upon physiological chemistry, and therefore, 
while admirably devised for teaching the student chemical methods, 
is not a legitimate part of a book devoted to botany. It occupies less 
than one-third of the volume. 
It is noteworthy that ecological topics, commonly included to a 
greater or less extent in works upon vegetable physiology, have been 
wholly excluded. ; 
A word of commendation is due the publishers for the neat and appro- 
priate way in which the printing and binding have been done. An 
excellent index increases the usefulness of the work. 
Alternation of generations. 
This subject has long been a prominent one in both botany and zo- 
ology, and a clear, incisive presentation of any part of it will be ac- 
ceptable to a large number of students. It is rare that any subject of 
such deep biological import and such wide reaching influence as this 
is more happily discussed and illustrated than in the recent work 
on gall flies and their production of oak galls by Dr. Hermann 
Adler, englished with valuable additions by Charles R. Straton. 
The alternate generations of gall-flies in certain species are very 
sharply marked, so much so that the sexual and agamic forms have 
been described under distinct genera. Mr. H. F. Bassett, of Con- 
necticut, was the first to point out the probable connection between 
the two states, or rather to indicate that certain monosexual species 
were genetically connected with apparently distinct bisexual species. 
It was due to the labors of Dr. Adler, however, to fully establish the 
fact, and to work out the details in a considerable number of species _ 
by means of careful and patient observations and cultures. 
The results have been of more than taxonomic importance. We 
_ have before us, in fact, a particularly clear and happy exposition of a 
number of topics which are commanding wide attention at the 
present time, such as the purposes of alternate generations, ad- 
vantages of parthenogenesis, function of polar bodies, and the 
transmission of hereditary characters. Whoever is enies in such 
_ topics should not fail to read this attractively written wo 
The botanist as well as the entomologist will Hin the ook tefl 
1ADLER, HERMANN: SSS gag! generations: a biological study of oak oe 
fes. Trans. and edited by Charles R. Straton. 12mo I 
col. plates. "Oxford, Clarendon ane 1894. Macm millan & Co., New ow 
American publishers. $3.25. 
