724 EXPERIMENT STATION RECORD. 



replies received, which numbered 1,033, it appears that in many locali- 

 ties but little attention is paid to keeping varieties pure, and many- 

 farmers use mixed, unknown, or local varieties of ordinary merit for 

 seed. The gradual acclimation of cereals through years of selection 

 and cultivation is claimed to have produced varieties much better 

 adapted to one zone than another, and upon this theory the author has 

 mapped the distribution of 15 varieties of corn, 13 of wheat, and 7 of 

 oats. 



Life zones and crop zones of the United States, C. H. Merriam 

 ( U. S. Dept. Agr., Division of Biological Survey Bui. 10, pp. 79, map 1). — 

 The present report is designed to explain the relations of the study of 

 the geographical distribution of the native animals and plants to prac- 

 tical agriculture. The bulletin is divided into four parts as follows : 

 (1) Eelations of the Biological Survey to practical agriculture, (2) life 

 zones of the United States — boundaries, native species, and important 

 crops, (3) laws of temperature control of the geographic distribution of 

 animals and plants, and (4) crop tables. 



The first part is a reprint from the Yearbook of this Department for 

 1897 ; part 2 discusses the life zones of the United States, their bound- 

 aries, native species, and important crops. As recognized by the 

 author, the life zones of the United States are 6 in number, with sev- 

 eral minor subdivisions. In the third part the author states his views 

 relative to the effect of temperature in controlling geographical distri- 

 bution of animals and plants, and gives the following law based upon 

 his investigations: "The northward distiibution of terrestrial animals 

 and plants is governed by the sum of the positive temperatures for the 

 entire season of growth and reproduction, and the southern distribu- 

 tion is governed by the mean temperature of a brief period during the 

 hottest part of the year." The sum of the positive temperatures is 

 secured by adding together for the entire growing period the average 

 daily temperature in excess of 0° C. (43° F.). The length of period 

 which controls the southern distribution has not been definitely deter- 

 mined, but it is thought to be approximately the 6 hottest consecutive 

 weeks. In the table showing the governing temperatures of zones, 

 instead of the sum of the normal mean daily temperatures above 6° C, 

 as stated, the figures given are those of the total temperatures for the 

 entire growing period. Attention has been called to this. 1 



In the fourth part of the bulletin the zone ranges are given for the 

 more important varieties of cereals, and for apples, apricots, cherries, 

 grapes, peaches, pears, plums, strawberries, nuts, etc. In compiling 

 these ranges it became apparent that some varieties extend over wide 

 areas, thriving in many zones, while a few are confined to a single 

 zone. 



On plant culture and plant diseases, M. F. Nilssen (Tidsskr. Norske Landbr., 5 

 {1898), No. 5, pp. 241-282). — Report of work doue by Swedish and Danish experi- 

 ment stations in plant culture and plant diseases. 



1 Science, n. s., 9 (1899), No. 212, p. 116. 



