August 5, 1904.] 



SCIENCE. 



177 



be very elastic, and every concession should be 

 accorded that may tend to secure to us the 

 essential features of the metric system, even 

 if we discard a good deal that its founders 

 thought desirable for the sake of consistency. 

 There is plenty of time yet to give this subject 

 mature consideration without undertaking the 

 role of either the optimist, the pessimist or 

 the prophet. w. Le Conte Stevejjs. 



Washington and Lee Univeesity, 

 July 8, 1904. 



The Development and Structure of Vegeta- 

 tion. Studies in the Vegetation of the 

 State [o/ Nehrasha'j, III. By Frederic E. 

 Clements. Lincoln, Neb., published by the 

 Botanical Seminar of the University of 

 Nebraska. 1904. Pp. 175. 

 In the present work Professor Clements has 

 had a double purpose, first, to give an account 

 of our present knowledge of the cardinal con- 

 cepts in the study of vegetation, viewed in the 

 light of their historical development, and 

 second, to give more exact organization and 

 classification to those ideas as well as greater 

 definition to their terminology. He treats the 

 idea of the association in its various phases, 

 and with its diverse bases; of invasion, with 

 its elements, migration, ecesis (or adjustment 

 to the habitat), influence of barriers, endem- 

 ism, polygenesis, kinds and manner of inva- 

 sion; of succession in its various phases; of 

 zonation; and of alternation, involving com- 

 petition. Each section has its bibliography. 

 Many interesting views are presented in the 

 courge of the paper, among others the opinion 

 that competition in plants has a purely phys- 

 ical basis, or, in other words,' that competing 

 plants influence one another only as physical, 

 . and not as physiological, agents. This view, 

 which it must be admitted is the only one 

 justified by facts at present at our command, 

 would make associations and other groups of 

 this nature merely physical mixtures of plants 

 with no organic connection between the mem- 

 bers (excluding parasites, etc.) ; but it is not 

 improbable that further research will show 

 this view to be incorrect. Another feature 

 of the paper is the attempt of the author to 

 give greater definition to the terminology of 



the subject, to which end he proposes many 

 new terms, all of which have the positive 

 merit that they are etymologically appropriate 

 and consistent. Whether or not these merits 

 will result in their adoption remains to be 

 seen, but Professor Clements's proposa;ls in 

 this as in his earlier works have the great 

 advantage of being first in the field. The 

 author also emphasizes the need for accurate 

 experimental and statistical field study as a 

 basis for further ecological advance, a matter 

 in which ecologists seem now to be in full 

 agreement. Altogether, Professor Clements 

 has given us a valuable and timely contribu- 

 tion to the study of this increasingly attrac- 

 tive subject, and his work is likely to exert 

 no small influence in its development. 



W. E. Ganong. 



Mineral Tahies. For Determination of Min- 

 erals hy their Physical Properties. By 

 Arthur S. Eakle, Ph.D., Assistant Pro- 

 fessor of Mineralogy, University of Cali- 

 fornia. New York, John Wiley and Sons. 

 8vo. Pp. Y2. 



The new features in these tables are the 

 prominence given to color as a classifying 

 character and the restriction to the considera- 

 tion of two hundred (approximately) common 

 species. Lustre is made very subordinate, the 

 divisions are by the ' streak,' color of the fine 

 powder, and the subdivisions by ' color,' color 

 of the mass. 



For minerals which crush to a colored 

 powder this affords an easy and generally ac- 

 curate separation. But the silicates of all 

 colors and many light-colored minerals yield 

 white powders and their distinction by phys- 

 ical characters alone is not easy in average 

 massive specimens, and this division extends 

 over two thirds of the entire book. No re- 

 source is made to blowpipe tests, the inference 

 to be drawn from a paragraph in the introduc- 

 tion being that ' blowpipe analysis ' should 

 follow as a separate feature of the course. 

 The time allotted to mineralogy in many col- 

 leges would hardly permit this, however. 



The omission of the rarer species and the 

 limitation of the necessary apparatus to knife, 

 magnet, lens, streak-plate and hardness scale 



