74 University of California Publications in Agricutlural Sciences [Vol. 2 



There is also the remote possibility that unfertilized pistillate 

 flowers might develop parthenogenetically, the egg-nucleus, 

 containing the haploid number of chromosomes, developing 

 spontaneously into an embryo. In order that such seeds should 

 produce only calif ornica individuals it would be necessary that 

 a single dose of the quercina factor could not condition quercina 

 development even in plants having the reduced number of 

 chromosomes. This is at variance with the concept that Men- 

 delian reaction systems depend upon proportional chemical 

 relations such that one dose of a recessive factor would play 

 the same role in an individual having a haploid system as two 

 doses of the same factor play in an individual having a diploid 

 system. Therefore, the former is the more reasonable inter- 

 pretation. 



(2) A PARALLEL MUTATION IN JUGLANS HINDSII 

 (JEPSON) SARGENT 



In November, 1914, through the courtesy of Farm Adviser 

 F. F. Lyons, my attention was called to a nursery at Modesto, 

 California, where there were several thousand one-year-old seed- 

 ling walnuts. Here and there among the typical black walnuts 

 I found a number of plants (fifty or more) that closely resembled 

 /. calif ornica var. quercina except that they were taller than 

 quercina seedlings of the same age and the leaves appeared 

 somewhat larger. Through the kindness of the owner, George F. 

 Covell, seven of these seedlings are now growing on the campus 

 of the University of California. These seven and several that 

 were examined at the nursery were found to have come from 

 typical nuts of J. hindsii, the northern California black walnut. 

 The trees that produced the nuts which Covell planted in his 

 nursery are also typical of J. hindsii, but as they had been grafted 

 to commercial varieties I was unable to secure seeds from them. 

 However these grafted trees are seedlings from four large north- 

 ern black trees growing near Lodi, California. Several hundred 

 nuts from each of these trees have been germinated and only 

 seedlings typical of /. hindsii have been secured. If any one of 

 these trees is repeating the mutation there is no evidence of it in 



