]913] Babcock: Neiv Form of Juylans 23 



by assuming that the pollen grains engaged in fertilization bore 

 J. calif ornica characters as a result of segregation in the reduc- 

 tion divisions. But it is as reasonable to explain these results 

 by assuming that the ovule-borne characters of J. californica 

 are dominant or prepotent over the pollen-borne characters of the 

 new form, supposing that fertilization actually took place. It 

 is obvious that more extensive experiments should be made in 

 an effort to secure reciprocal crosses between the species and the 

 variety. 



Webber has expressed the following opinion : " Of the various 

 causes of origin it seems to me most reasonable to assume that it 

 is a mutant and the type of mutation to nanate form is similar 

 to Oenothera nanella and the Cupid Sweet Pea. One finds par- 

 allel cases of partial reversion to the parent type among De 

 Vriesian mutations." 



The reasons for thinking the new form may have originated 

 through mutations in otherwise normal flowers of J . californica 

 may be stated briefly as follows : 



1. In the 1911 recurrence of the new form in Garden Grove, 

 it was found by actual examination of the seed bed that all of 

 the aberrant seedlings examined grew from nuts of normal size 

 and shape. 



2. The crop of 1912 from a certain tree of Juglans califor- 

 nica (No. 16 in the Garden Grove row above mentioned) has 

 produced several seedlings of the new form. The nuts from 

 which they grew are of normal size and shape. The possibility 

 of hybridization with any species of oak or other species of 

 walnut is very remote. 



3. The large tree standing close to No. 16 is known to have 

 been the source of many of the nuts planted in Tyler's nursery 

 in the years when quercina seedlings appeared in his seedbeds. 

 On this account it was suspected of being the source of the new 

 form. It appears, however, that No. 16 has been the source of 

 some quercina seedlings and that the particular seeds that gave 

 rise to it were produced on the branches nearest the tree origin- 

 ally siLspected. 



Transmitted May 9, 1913. 



