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THE AMERICAN NATURALIST [Vol. XLIV 



ditions, for example) as being not necessarily adaptive and in 

 any event not capable of being transmitted to offspring. He 

 believes, however, that what has been observed to take place 

 under experimental conditions might take place when plants or 

 generations of plants are subjected to the stimulus of desert en- 

 vironment. His words are : 



The influence of external conditions upon the germ plasm, however, 

 has been seen to produce irreversible changes in a hereditary line by 

 which new combinations of qualities and new characters were called 

 out, which were fully transmissible. Furthermore the newly produced 

 forms perished in some localities endured by the parental type, but 

 exceeded it in weathering the conditions of other localities. 



In the treatment of the larger aspects of the question of the 

 origin and movements of desert plants the intensive study of a 

 single small area fails to furnish a large enough fund of com- 

 parative data to make a wholly satisfactory basis for conclu- 

 sions. The reviewer would modestly suggest that the Sonoran 

 desert (meaning the desert areas of our southwest and of north- 

 ern Mexico) is a very large and diverse region in which not 

 merely individual species but whole genetic groups have become 

 xerophilized ( with apologies for spurious coinage), and that cor- 

 related investigations at numerous points and a study of genetic 

 relationships in connection with distribution, association, move- 

 ments and modification (meaning transmissible qualities or char- 

 acters) would furnish a broader basis for the interpretation of 

 the ways of plants in the desert at large. 



In a final word the reviewer would invite attention to the 

 status of Professor Spalding's book considered in relation to 

 plant ecology. In full appreciation of other recent ecological 

 contributions of similar merit the opinion is advanced that 

 this book stands in a special way as an index of the new era 

 in geographic ecology in which a field of botanical research 

 which was prone to abound in verbosity and in the discovery of 

 "adaptations" has been brought to the status of a more exact 

 science employing quantitative methods of study. It is not 

 boastful to say that this newer phase of plant ecology repre- 

 sents especially the outcome of the teaching and investigations 

 of a small group of American botanists (of which group the 

 present reviewer can not claim to be a member) who have sought 

 to put the study of plant relations upon the same basis as that 

 pursued in the study of plant physiology in the limited sense. 



William L. Bray. 



