274 BOTANICAL GAZETTE [april 



been excluded, and vice versa. The natural rhythm of response may he increased 

 or diminished, provided the latent period of the organ is less than the daily period 

 of hght and darkness. 



This work is one that will be needed in every active laborator)', so that any 

 more detailed statements of its conclusions would be superfluous. — C. R. B. 



NOTES FOR STUDENTS 



Plant breeding.— Bulletins of the various Agricultural Experiment Stations 

 usually deal with the practical side of agricultural problems, and there has not 

 been at all times a recognition of the practical value of theoretical matters emanat- 

 ing from pure scientific sources. 



purpose 



in which a well-written review of the development of the evolution idea is given, 

 along with the more recent developments in our knowledge of variations and of 

 heredity. In the main the treatment is well balanced, but in some respects there 

 is too obvious a leaning on Morgan's recent publications. Particularly does it 

 seem out of place, in so brief a paper, to present Morgan's theory of the impurity 

 of the gametes— a theory which has lost practically all the slight support it seemed 

 to have when first propounded. 



It is noted on p. 68 in the discussion of the Belgian-hare cross, as an illustra- 

 tion of "masked" characters, that the older explanation is retained, based upon 

 the supposed presence of a black factor in the albino. Castle^ has ^given a 

 more satisfactory explanation of such cases by assuming an "agouti factor" which 

 distributes the pigment in distinct regions in each hair, giving a grey effect. The 

 Belgian hare of the experiment cited had both dominant characters, namely pig- 

 ment and agouti, and the albino lacks them both. The advantage of Castle s 

 explanation lies in the fact that it brings such cases into harmony with the "pres- 

 ence and absence" hypothesis which has found such wide support in other cases 

 and to which the author of the bulletin himself subscribes. 



The section on "Methods of plant improvement" is doubtless the most valu- 

 able part of the paper. Its scope may be indicated by the subheads: "The selec- 

 tion of fluctuations," "Isolation of elementary species," "Judging plants by their 

 progeny," "Correlated characters," "Improvement by hybridization." Unde^ 



the first of these subheads a valuable summary is given of the results gained by 

 w^..-...„ „_. V. . . . the breeding 



associates at the Illinois Experiment 



of maize for high and low protein and high and low oil content. The crop averages 

 for ten years are given, showing that in this time the maximum separation of the 

 extremes with respect to these characters seems to have been attained. 



■ 3 East, E. M., The relation of certain biological principles to plant breeding- 

 ^onn. Agric. Exp. Sta., Bull. 158. pp. 93. figs. 6. 1907. 



^ Castle, W. E., On a case of reversion induced by cross breeding and its bxa- 



Science N. 5.25:151-153. 1907. 



