GENETICS: E. B. BABCOCK 
535 
WALNUT MUTANT INVESTIGATIONS 
By Ernest B. Babcock 
DEPARTMENT OF AGRICULTURE. UNIVERSITY OF CALIFORNIA 
Presented to the Academy. August 20, 1915 
About fifteen years ago there appeared in a nursery of Southern 
Cahfornia Black Walnut seedlings a new and very distinct form of 
Juglans. Two of the original trees still stand where first transplanted 
from the seed bed. These are the type specimens which I described^ 
and named Juglans californica var. quercina because of their general 
resemblance to a small-leaved oak. Similar seedlings have been secured 
from two other trees of Juglans californica Wats. In 1914 seedKngs 
of this same oak-like type appeared in a nursery of the Northern Cali- 
fornia Black Walnut, /. californica var. hindsii Jepson. This is a very 
interesting parallel mutation because hindsii was originally described 
as a species^ and is separated from californica by several distinct features. 
However, this occurrence of parallel mutations does not in itself necessi- 
tate any change in nomenclature other than to designate quercina as 
mutation rather than variety. Therefore I propose to designate quer- 
cina individuals produced from seeds of /. californica as /. californica 
mut. quercina and to similar individuals produced from hindsii seeds as 
/. californica var. hindsii mut. quercina. 
In 1910 I discovered that many otherwise normal trees of Southern 
California Black Walnuts produce a second crop of flowers, from one to 
two months later than the first crop and that these nuts are invariably 
teratological.^ However, up to 1913 all the plants produced by the 
teratological nuts collected resembled J. californica, i.e., there was no 
evidence that teratology was the cause of the origin of quercina. 
In 1912 I was able to locate an apparently normal tree of Juglans 
californica Wats., which produces a small percentage of quercina seed- 
lings each year and to learn that these grew from normal nuts. This 
tree is designated as Garden Grove No. 16. It is probably the only 
perennial mutating individual accessible for experimentation. That 
the mutation always occurs in the pistillate flowers is shown by the 
fact that Garden Grove No. 16 is the only tree in a row of 21 (all of which 
were tested in 1912) that produced quercina seedhngs. An objection 
has been raised to the designation of Garden Grove No. 16 as a mutating 
individual. The argument advanced is based on the assumption that 
all new types of organisms are due to recombinations of genetic factors 
and hence that if Garden Grove No. 16 produces two types of seedhngs 
