UNIVERSITY OF CALIFORNIA PUBLICATIONS 



IN 



AGRICULTURAL SCIENCES 



Vol. 2, No. 2, pp. 47-70, pis. 13-19 October 31, 1914 



STUDIES IN JUGLANS II 



FURTHER OBSERVATIONS ON A NEW VARIETY OF 



JUGLANS CALIFOBNICA WATSON AND ON 



CERTAIN SUPPOSED WALNUT-OAK 



HYBRIDS 



BY 

 ERNEST B. BABCOCK 



In the preceding paper on this subject^ appeared the history 

 and description of a new form of California Black Walnut, which 

 was named Juglans californica var. quercina, together with a 

 discussion of several hypotheses regarding its nature and origin. 

 The following hypotheses were deemed worthy of serious consid- 

 eration and feasible as bases for further study: 



(1) Origin through hybridization with the Coast Live Oak, 

 Quercus agrifolia Nee. 



(2) Origin from teratological flowers and fruits of /. cali- 

 fornica. 



(3) Origin by mutations in apparently normal flowers and 

 fruits of J. californica. 



In order to test the first hypothesis, that of origin through 

 hybridization between walnut and oak, attempts to hybridize the 

 two species were made in the years 1908 to 1911, inclusive. As 

 a result of the pollination work in 1908, fifty-six seedlings were 

 secured from nuts that developed from pistillate walnut floM^ers 

 which had been pollinated with oak pollen under bag. Except 

 for considerable variation in size, these trees have not exhibited 

 more differences than would be found among ordinary trees of 



