May 26, J 899.] 



SGIENGE. 



749 



prairies or steppes aud deserts is, of course, 

 primary aud affords au altogether satisfactory- 

 basis for the arrangement of the formations. 

 The statement that the constitution of the floral 

 covering is determined by the three factors, 

 temperature, hydrometeors and soil, is axio- 

 matic; one is inclined, however, to give only 

 partial assent to the conclusion that temperature 

 determines the flora, hydrometeors the vegeta- 

 tion, and soil composition the formation. The 

 analysis of the determining factors of forest, 

 prairie aud desert vegetation is excellent. 

 Moderate frequency of precipitation is of first 

 importance for forest vegetation. A rainy 

 growing period is less favorable, the primary 

 requisite being considerable water content in the 

 soil, especially at some depth. The time of year 

 in which the water supply is replenished is unim- 

 jjortant. The latter may occur throughout the 

 year or only periodically. In the last case the 

 rainy season may coincide for the most part, or 

 entirely, with the growing period, as in the 

 tropics and in the interior of Argentina, or 

 with a period of relative rest, as in extra-trop- 

 ical regions with wet winters, Mediterranean 

 countries. Chili, California, south and southwest 

 Australia. Forests are limited only by such 

 degrees of dryness as prohibit all other vegeta- 

 tion, with the exception of fungi and alga. The 

 polar limit of forested areas is determined by 

 dry winds during the season of frosts. Sum- 

 marizing, a climate favorable to forestation 

 presents the following conditions : warm grow- 

 ing period, constantly moist substratum, moist, 

 quiet atmosphere, particularly in winter. It is 

 unimportant whether the water content of the 

 soil is supplied from meteoric or telluric sources, 

 whether the precipitation is frequent or rare, 

 coincident with the growing period or the period 

 of rest. A climate with dry winters is unfavor- 

 able to forests in the highest degree, since the 

 trees are unable to recover from the transpira- 

 tion loss of the winter. 



For prairies and steppes a moist substratum 

 is unimportant, but a moist upper surface is 

 essential. The most favorable conditions for 

 grass vegetation are frequent, if only slight, 

 precipitation during the growing period aud 

 concomitant moderate warmth. Prairies are 

 affected little by the moisture of the substratum. 



except in the case of extreme capillarity of the 

 surface, by the dryness of the air, especially 

 during the period of rest, and by winds. Dry- 

 ness in the maximum of the growing period, 

 spring and early summer, is inimical, in a high 

 degree, to grass vegetation. Axiomatically, in 

 a climate favorable to forestation, forests pre- 

 dominate ; in one favorable to grasses, prairies 

 and steppes are the rule. In transition regions 

 predominance is determined by adaptation to 

 edaphic factors. Extreme departures from the 

 mean favorable to forest or to prairie vegeta- 

 tion produce deserts. 



It is impossible even to touch upon the third 

 part of the volume, which constitutes by far the 

 largest portion. It deals with the zones and 

 regions of the vegetative covering of the earth. 

 The latter is treated in the most exhaustive 

 manner since Grisebach under the captions : 

 tropical zone, temperate zone, arctic zone, 

 montane regions and hydrophytic formations. 

 Each zone is considered in a very logical man- 

 ner with reference to the three main manifesta- 

 tions of the vegetation, forest, prairie aud 

 desert. The high value of the text is greatly 

 enhanced by the large number of fine illustra- 

 tions. It seems impossible to commend too 

 highly this marked feature of the book. It may 

 be regarded as significant of the time when 

 phytogeographical results will be embodied, for 

 the most part, in graphic fashion, in photo- 

 graphs, abundance-frequence indices aud charts, 

 aud formational lists and contrasts. 



Frederic E. Clements. 



The Ukiveesity of Nebraska. 



Victor von Bichter's Organic Chemistry. Edited 

 by Professor R. Anschutz, University of 

 Bonn. Authorized Translation by Edgar F. 

 Smith, Professor of Chemistry, University of 

 Pennsylvania. Third American from the 

 eighth German edition. Vol. I., Chemistry 

 of the Aliphatic Series. Philadelphia, P. 

 Blakiston's Sons & Co. 1899. Pp. 625. 

 Price, $3. 



Anschutz, in editing v. Richter's 'Organic 

 Chemistry,' has raised it from the rank of a good 

 descriptive manual to a place in the front rank 

 of books on this subject. He has had the aid of 

 Emil Fischer in the supervision of the chapters 



