216 



The definition of adsorption, on page 440, restricts it to the re- 

 duction of toxicity by solid particles. 



In Chapter XVI, on "The Temperature Relation," the im- 

 portance of the length of the growing season (the period between 

 the last killing frost of spring and the first one of autumn) is not 

 emphasized. All temperatures are given in degrees Centigrade, 

 and no reference is made to Professor Abbe's work of 1905. 



The statement on page 468 that "great diversity of opinion 

 prevails with regard to the magnitude [sic] of the variations by 

 means of which progress in selection is maintained," tends, in the 

 light of the preceding paragraph, to perpetuate the error that 

 the difference between mutation and fluctuation is one of degree; 

 and the assertion on page 469, that "Many deny permanence to 

 this type of selection" (of fluctuating variations in sugar-beets) 

 seems quite too mild, in view of recent work. 



On page 474 it is stated that "the extreme supporters of the 

 mutation principle . . . actually exclude the possibility of any 

 such phenomenon as transmissible fluctuation," yet de Vries, 

 himself, has said* that "The answer to the question whether 

 acquired characters are inherited, is that they are not so in their 

 entirety, but with a reduction, the amount of which is indicated 

 by Galton's law"; and he later calls attention to the fact that 

 if there were no inheritance of fluctuating variation, the improve- 

 ment of horticultural races would not be possible. 



The laboratory directions at the end of each chapter are well 

 adjusted to the text, and especially so to the class of students for 

 whom they are intended. One wonders, though, how many 

 hours of credit should be allowed the poor "Agric." who is re- 

 quired (p. 378) to "make a careful count of the number of 

 blossoms produced" by an apple tree! A number of investi- 

 gators would be glad to learn how to determine "the moment of 

 wilting" of a plant (p. 62); and a knowledge on the part of the 

 student of the precautions necessary in order to weigh a number 

 of slightly wilted leaves "accurately upon a delicate balance" 

 (p. 63) can hardly be taken for granted. On pages 223 and 224 



* De Vries, Hugo. The Mutation Theory. Eng. Translation. Vol. II, p. 136. 

 1911. 



