16 University of California Publications in Agricultural Sciences [ Vol. 2 



In 1908 the check results were much more satisfactory thau 

 in 1911. Various factors may have influenced these results, but 

 the writer is inclined to think that the comparative isolation of 

 the Los Angeles trees made them more satisfactory subjects for 

 experimentation. From the 1911 results we find nearly as hi^h 

 a percentage of nuts in check bags as in pollinated bags from 

 Tree A and a higher percentage from Tree B. Tlie production 

 of nuts in the check bags raises the question of the po.ssibility of 

 apogamic development of seed in Juglans calif ornica, and throws 

 a shade of doubt upon the supposed hybrid seedlings that have 

 been obtained from oak pollinations. In this connection more 

 experimental work should be done in preventing natural pollina- 

 tion on a large scale. 



For the present the writer is inclined to think that one of 

 the other two hypotheses is much more likely to reveal the origin 

 of our new form. Dr. Cannon, of the Desert Laboratory. Car- 

 negie Institution of Washington, who is an authority on plant 

 hairs, informs me that he finds no evidence of oak characters 

 in the hairs of Disher's original trees. 



Second Hypothesis 



Let us consider next the possibility that the new form may 

 originate in certain teratological flowers on certain Juglans cali- 

 formca trees. It is necessary to give here a brief account of 

 the discovery of these abnormal flowers and to state the reasons 

 for considering them as a possible source of the new form. In 

 order to emphasize the teratological features about to be described, 

 it may be well to consider first the characteristics of normal fruits 

 and flowers. Normal flowers are shown in plate 6, figure 10. 

 Normal leaves and fruits are shown in plate 7, figure 11. 



The normal blooming period of most wild black walnut trees 

 in southern California is in April. As the staminate catkins are 

 produced upon the wood of the previous season's growth, their 

 gradual increase in size may be observed at any time during late 

 winter or spring. During March they lengthen noticeably. 

 About April first the pistillate catkins appear, terminating the 

 first new growth of the season. They are one or two inches 

 long and bear one to five flowers, so that, when the fruits mature, 



