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symbionts is not benefited because no assistance is required. As 
an example may be mentioned the mycorhiza of certain trees and 
the mycodomatiae (rhizobia) of Leguminosae. Here the author 
supposes that the infecting fungus works in the interest of the 
plant infected without receiving any benefit in return. 
In Part I. are also given various approved methods and means 
for guarding against infection of pernicious parasites and how to 
to destroy them after infection has taken place. 
Part II., which is by far the most extensive, treats of “ phyto- 
pathogenic fungi and algae.” It is essentially a systematic de- 
scription of the infecting fungi and algae based upon the most re- 
cent investigations and conclusions. 
Taken all in all, this work is certainly a most valuable contri- 
bution to the science of botany. It will prove of great benefit to 
all botanists. The condensed retrospect of the subject will suffice 
for the general student, while the citations will be found very useful 
by the special student. 
Language and style are scientifically clear and simple. Only a 
a few of the figures are borrowed. ALBERT SCHNEIDER. 
A Monograph of the North American Species of the Genus Poly- 
gonum, by John Kunkel Small. This work, a folio of 183 pages 
(not counting the plates), was issued on the 23d of April, 1895, as 
the first volume of Memoirs from the Department of Botany of 
Columbia College. 
In the introduction, after discussing the position of the family 
to which it has given a name, the relation of the genus Polygonum 
to its allies is taken up and considered. Then follow chapters on 
the geographical distribution of the species, the general morphol- 
ogy of the genus, the anatomy of the stem and general anatomy. 
Natural and distinct as the genus appears, it admits of division 
into well-marked sub-genera, nine of which contain representa- 
tives in the New World, viz.: Bistorta, Aconogonon, Persicaria, 
Amblyogon, Tovaria, Avicularia, Duravia, Tiniaria and Echino- 
caulon. These, as described and figured by Dr. Small, including 
a fossil species from the Miocene Tertiary of Colorado, number 71. 
Each of them is illustrated by an uncolored outline-drawing on a 
separate sheet, so admirably executed as to make the salient charac- 
