152 University of California Publications in Botany [Vol. 5 



ratio may be due to the small number of plants grown in F2, 

 while in the other case we have difficulty in interpreting the 

 wide variations in the outward evidences of such segregation as 

 was observed to occur in F^, in terms of any Mendelian scheme 

 of analysis. 



In general, both experiments are concerned with the "ques- 

 tion of the inheritance of bulk" (Darbishire. 1911, p. 241) in 

 reference to which, as this same writer states, ''the present 

 available information is very scanty." We are thus justified 

 in not endeavoring to formulate definitely any general hypotheses 

 on the basis of our experimental evidence, but have attempted 

 to suggest, merely tentatively, certain points of view which seem 

 applicable to the problems in hand. 



It is a pleasure to acknowledge my indebtedness to Prof. W. 

 A. Setchell, at whose suggestion the experiments were under- 

 taken and under whose direction they have been carried on, 

 for much helpful advice and criticism ; to the Department of 

 Physiology of the University of California for placing at my 

 disposal the use of the mechanical balances used in weighing the 

 hybrid tobacco seed ; to Mr. Sturla Einarsson of the Department 

 of Astronomy for providing me with the Monthly Meteorological 

 Keports of the Students' Observatory which are combined to 

 form the table on page 124; and to the members of my family 

 for much assistance in connection with the measurements of the 

 corolla diameters of hybrid tobacco flowers and in preparing the 

 manuscript for the press. 



LITERATURE CITED 



Bateson, W. 



1909. Mendel's Principles of Heredity. Cambridge University Press. 



Baur, E. 



1911. Einfiihrung in die experimentelle Vererbungslehre. Gebruder 

 Borutraeger. Berlin. 



Blaeingheim, L. 



1911. La notion d 'espeee et la disjonction des hybrides, d'apres 

 Charles Naudin. Prog. Rei Bot., vol. 4, part I, pp. 27-108. 



Brainerd, E. 



1907. Mendel's Law of Dominance in Viola. Rhodora, vol. 9, p. 211. 



