UNIVERSITY OF CALIFORNIA PUBLICATIONS 



IN 



AGRICULTURAL SCIENCES 



Vol. 2, No. 3, pp. 71-80, plates 20-21 September 20, 1916 



STUDIES IN JUGLANS, III 



(1) FURTHER EVIDENCE THAT THE OAK-LIKE 

 WALNUT ORIGINATES BY MUTATION 



BY 



ERNEST B. BABCOCK 



In previous studies 1 the conclusion was reached that the oak- 

 like walnut, Juglans calif ornica var. quercina Babcock, was first 

 produced as a result of germinal variation in a tree of the 

 southern California black walnut, J. calif ornica Wats., and that 

 the several recurrences of this peculiar walnut resulted from 

 repetitions of the same mutation. It is the purpose of this 

 paper to report further evidence showing that this conclusion 

 was correct at least as regards the origin of the first quercina 

 individual, although this same evidence may lead to a different 

 explanation of some of the recurrences of this form. 



This evidence consists of the results from hybridizing quercina 

 and calif ornica. In 1908 pollen from the original, fertile, type 

 individual of quercina was applied to several guarded pistillate 

 flowers on a typical calif ornica tree. The eleven F x seedlings 

 secured are growing on the campus of the University of Cali- 

 fornia. They are all normal calif ornica trees. The only evidence 

 of heterosis thus far observed is length of staminate catkins, 

 which is intermediate between the two parents. In 1915 several 

 of these F l trees were self-pollinated, or interpollinated, and 

 thirty-six seeds were secured. Up to the present eighteen of these 

 have germinated, producing twelve calif ornica and six quercina 



i Babcock, E. B., Studies in Juglans I and II, Univ. Calif. Publ. Agric. 

 Sciences, vol. 2, no. 1, 1913; no. 2, 1914. 



