1918.] HORTICULTURE. 747 



" The observations and experiments recorded . . . justify the tentative con- 

 clusion that unfavorable conditions of nutrition and water supply are among 

 the basic factors which cause the normal drop of flowers and partially devel- 

 (jped fruits of the apple. All factors that have a direct or an indirect influence 

 on nutrition and water supply of the flower and the fruit, sucli as pollination, 

 weather, cultivation, and the like, are of importance. Fruit development, how- 

 ever, is possible without cross-pollination and even under relatively unfavorable 

 weather conditions, so long as the young fruit has an abundant supply of water 

 and of readily available food." 



The comixion honeybee as an agent in prune pollination, A. H. Hendbick- 

 SON {California Sta. Bui. 291 (1918), pp. 215-236, figs, i.3).— In some tent ex- 

 periments conducted in 1916 (E. S. R., 36, p. 536) it was shown that bees are 

 a necessary aid to pollination with the French and Imperial varieties of prunes. 

 The study was continued on a larger scale in 1917 and is here reported on in 

 detail. The tent experiments were so arranged as to test the effect of the 

 absence of pollen-carrying agents, to study the question of interfertility or the 

 necessity for interplanting for purposes of cross-pollination between the two 

 varieties, and to determine the ability of each variety to set fruit with its own 

 pollen. Counts were also made of the blossoms of each vaiiety on trees growing 

 in the open, in order to get the set of fruit that occurred under average orchard 

 conditions. 



Summing up the results of the two seasons' work, the author concludes that 

 " both the French and Imperial prunes may be aided in setting fruit by the 

 use of bees in the orchard during the blossoming period, provided the trees are 

 in a normal, healthy condition. The absence of bees in the orchard may mean a 

 low percentage of set with both of these varieties. The French prune does not 

 absolutely require interplanting with the Imperial, even though this arrange- 

 ment may prove beneficial to both varieties." 



Pruning- the seedless grapes, F. T. Bioletti {California Sta. Circ. 191 

 {1918), pp. 12, figs. 10). — This circular contains specific directions for the 

 methods of pruning which have given the best results with seedless raisin 

 grapes. Information is given relative to the treatment of young vines, trellising, 

 and pruning bearing vines. 



The mango in Porto Rico, C. F. Kinman {Porto Rico Sta. Bui. 2Jf {1918), 

 pp. SO, pis. 11). — This bulletin embodies the more important results relative to 

 mango culture in Porto Rico, based upon several years' work at the station 

 during which trees of many varieties have been imported, propagated, and in 

 some cases brought into satisfactory production. The important phases dis- 

 cussed include the soil and climate of Porto Rico, with special reference to 

 mango growing, blossoming period, propagation, importance of classification, 

 desBcription of varieties, weights of different parts of fruits, protection against 

 fruit flies, harvesting and packing, and mangoes as ornamentals. 



The investigation as a whole has shown that imported varieties of mangoes 

 superior to the common mango of Porto Rico can be grown successfully in prac- 

 tically all Porto Rican soils, provided that there is a good subdrainage and that 

 they should be planted extensively for market and home use. Good crops are 

 more certain along the western and northern lowlands of the island where the 

 rainfall is light during the blossoming season. The prevailing winds and morn- 

 ing sun seem to be very beneficial both for the growth of the trees and setting 

 of fruit ; hence open, exposed sites should be selected for the orchard. Propaga- 

 tion both by inarching and by bark grafting has proved satisfactory for use 

 in the nursery and for top working large trees. Large seeds which produce 

 only one plant are most satisfactory for stocks. The East Indian varieties pro- 

 duce larger and more thi-ifty plants as a rule than the native mangoes. Both 



