THE OAK-WALNUT MUTATION 



Figure 1.']. The oak walnut is a ipeculiar mutation of the native California walnut 

 (Juc/laiis Calif ornica), so distinct from the parent type as to have been described as 

 a distinct species, JugJans qucrcina. When first discovered it was supposed to be a 

 walnut-oak hybrid, on account of the peculiar shape and the thick leathery texture of 

 the leaves. (See Babcock, E. B., A New Walnut, Journal of Heredity, Vol. VI, p. 40). 

 Some of the leaves are si'mple with only one pair of lateral pinnae, but most of the 

 leaves have two pairs of pinnae. The small size of the leaves and the reduced number 

 of pinnae may be explained by analogy with the intermediate or bud-scale leaves of 

 other members of the family, but complete suppression of the normal compound leaves 

 is remarkable. A variety of the Persian walnut has also been described under the 

 name Juglans nionophylla to which the California oak-walnut may be analogous. A 

 tree of the oak-walnut at the U. S. Plant Introduction Garden at Chico, California, 

 bore a large crop of ripe fruits in September, 1922. Many of the fruits were twinned, 

 mostly with separate nuts, but in some the shells of the two nuts were grown firmly 

 together, as shown at the top of the photograph. (Natural size). 



