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the plants have come from moderate elevations in one portion 
of a great continent. The work will be of much value to botan- 
ical workers in many countries other than that for which it is 
primarily intended.—C. B. ROBINSON. 
SMITH'S BACTERIA IN RELATION TO PLANT DiskEAsEs.*— This 
is the second volume of Dr. Smith's publication and follows the 
first after an interval of six years. The earlier part discussed 
the general properties of bacteria, the methods of bacteriological 
research and so on. It has also proved to be a store-house of 
useful data and bibliographies. The present volume deals 
more particularly with the problems of the bacterial pathology 
of plants, with special reference to the vascular diseases. A 
great deal of space is given to the consideration of such subjects 
as the channels of infection in plants, the nature of parasitism, 
immunity factors, the normal bacterial flora of higher plants, and 
plant hygiene. All of these topics and many more are handled 
in the author's chatty and interesting manner. His own high 
position in his science makes it possible for him to speak in a 
personal way of many things, for there are few phases of the 
subject that he has not studied in his long and active career. 
The difficulty he once found in obtaining recognition for the idea 
that bacteria may cause disease in plants is echoed in the fol- 
lowing paragraph quoted from him. 
“The objections to bacterial parasitism in plants have been 
objections coming from those not familiar with such phenomena, 
and we all know how difficult it is at first for new ideas to make 
their way. Such things could not happen because they had not 
come within the ken of the objector, or because the physical 
nature of plant-tissues offered (theoretically) an insuperable 
obstacle to their multiplication, or because plant juices were acid 
and all known bacteria required an alkaline medium, or because 
if such diseases existed, one would already have discovered them. 
All of these objections were the result of inductions based on 
insufficient evidence. A thousand observations, let us say, con- 
* Smith, Erwin F. Bacteria in Relation to Plant Diseases, Vol. II, pp. 1-368. 
Publication 27, Vol. II, Carnegie Institution of Washington. отг. 
