1917] HORTICULTURE. 139 



ing the importance of selection as to variety if the percentage of oil is to be 

 talien into consideration. Demonstrations made by Coit show that the Babcock 

 test may be used for the determination of fat in avocados with sufficient accu- 

 racy for a preliminary comparison of the value of seedlings. 



Preliminary examinations by Jaffa of olives labeled " ripe olives " show a 

 variation in the fat content much greater than can be ascribed to tlie difference 

 in varieties or to the loss of oil in the pickling process. The wide range is con- 

 sidered to be largely due to the processing and marketing of immature olives 

 in place of ripe olives. 



The more important practical results secured from grape investigations con- 

 ducted by F. T. Bioletti are summarized. The plum and prune pollination In- 

 vestigations carried on by A. H. Hendrickson show definitely that all varieties 

 of the Japanese prune or plum (Prunus triflora) are self -sterile, with the pos- 

 sible exception of the Climax. The varieties of this group seem to cross-polli- 

 nate readily. Of the European varieties of plum, P. domestica, Tragedy, and 

 Clyman show distinct evidence of self-sterility. Of the prunes, French and 

 Sugar prunes appear to be self-sterile to some extent. Robe de Sergeant and 

 Imperial prunes are distinctly self-sterile. Imperial, French, and Sugar prunes 

 seem to cross-pollinate satisfactorily. 



In similar observations on almonds made by W. P. Tufts during 1916 13 

 varieties, including practically all grown on a commercial scale in California, 

 proved to be wholly self-sterile under conditions existing at the University 

 Farm. Two of the leading varieties. Nonpareil and I X L, were found to be 

 intersterile as well as self-sterile. Ne Plus Ultra was satisfactory as an inter- 

 pollenizer vrlth both I X L and Nonpareil. 



The leading commercial varieties of cherries grown in the State, including 

 Napoleon, Lambert, Bing, Black Tartarian, and Black Republican, were found 

 to be self-sterile. There is distinct evidence of intersterility between several 

 varieties, such as Bing and Napoleon. The best pollenizers for cherries in 

 the State have not been worked out thus far. 



Preliminary investigations conducted by W. L. Howard and Tufts indicate 

 that fruit bud formation under interior valley conditions, at least in California, 

 occurs from one to two months later than in other sections of the United States 

 where studies of this phase of fruit production have been made. 



Obsei'vations on the varieties of pecans planted in California indicate tliat the 

 season is too short for pecan culture in the northern and middle coastal regions. 

 In the interior valleys and in the southern coast counties many pecans have 

 been found to ripen their crops without difficulty. Many other pecan seedlings 

 failed to mature their crops in the southern coast counties. 



A study of the Weather Bureau records in various parts of California by A. E. 

 Way for determination of maturity of oranges have led him to conclude that 

 the factor that chiefly affects maturity is not soil type, irrigation, fertilization, 

 heat, or light units alone but the ratio between the total heat units and rela- 

 tive humidity of the atmosphere. 



A paper on the results of experiments in fertilizing citrus groves has been 

 noted from another source (E. S. R., 35, p. 448). The experiments in using 

 winter cover crops as green manures in citrus groves continue to emphasize 

 the importance of this practice in citrus culture (E. S. R., 33, p. 642). The 

 use of bitter clover (McliJotns indica), advocated by the station as a result 

 of these experiments, is becoming very general. The experimental plats on 

 the station grounds show marked increases in vigor and yield where green 

 manures have been used. 

 76601°— 17 4 



