842 EXPERIMENT STATION RECORD. 



In part 1, under the general heading of culture and uses, consideration is 

 given to the natural requirements of papayas, propagation, transplanting large 

 trees, irrigation, fertilizers, pruning in relation to change of sex, thinning 

 the fruits, artificial feeding, renewing the plantings, the frut crop, varieties, 

 the papaya as a food (including recipes), medicinal and other uses, and 

 papain, collecting the juice and preparing crude papain. Part 2 of the bulletin 

 comprises a progress report on the work thus far accomplished in the attempt 

 to secure improved strains of fruit by breeding. The subject matter is dis- 

 cussed under the following general headings : Botanical names, common names, 

 botanical relationships, descriptions of forms of papaya, summary of forms, 

 significance of the forms, change of sex, origin of different forms, origin of the 

 dioecious Carica papaya, breeding with the dioecious forms, breeding the her- 

 maphrodite forms, hermaphroditism in Lychnis dioica, breeding within the 

 andromonoecious forms, crossing the different forms, parthenocarpy, partheno- 

 genesis, hybridization of Carica, an attempt to breed a hermaphrodite papaya, 

 and ideals in breeding the papaya. A brief note on insect pests by D. T. Full- 

 away is also included. 



The authors here recognize 13 forms and combinations in which the papaya 

 occurs, with reference chiefly to the distribution of sexes and the shape of 

 the fruit. Some of these forms are not constant, whereas others are distinct 

 and have a practical bearing upon the subject of breeding. Of these latter the 

 most important are the male and female of the dioecious papaya together with 

 2 andromonoecious forms and 2 hermaphrodite forms. With reference to 

 inconstant forms the most primary change of sex which takes place is to be 

 observed in the appearance of hermaphrodite flowers on trees that have pre- 

 viously produced only staminate inflorescence. This fruiting of the male 

 papaya takes place most freely in cool climates outside the Tropics or at high 

 altitudes. Aside from the influence of climate on change in sex there are 

 many references In the popular literature of the papaya to the acquiring of 

 fruit-bearing habits by the male tree due supposedly to some injury such as 

 removal of the terminal bud or the breaking of the roots in transplanting old 

 male trees. lorns reported a case of this kind in which female flowers ap- 

 peared on male trees as a result of the removal of the terminal bud. He con- 

 cluded, however, that other conditions than the loss of the terminal bud must 

 be present and suggested that the trees may pass through cycles of develop- 

 ment (E. S. R., 20, p. 444). In another authenticated instance reported by 

 J. T. Gulick female flowers with resulting fruit developed on a male tree 

 which had been beheaded. Since methods such as these do not bring about 

 similar results unfailingly, the authors conclude that certain unknown condi- 

 tions are present, and suggest that the phenomenon may be due to bud varia- 

 tion. No record has been found which would indicate that the strictly female 

 or pistillate tree has ever changed its sex. Some of these changes in sex when 

 they have been brought about tend to reproduce themselves in the offspring of 

 such plants, 



A study of the diflSculties which are met with in using the dioecious type 

 for breeding purposes has led the authors to work principally with the her- 

 maphrodite forms. The results of this work thus far show that it is possible 

 by using a hermaphrodite parent to do away with the very large proportion 

 of male trees which usually result from dioecious seed. Seed of one her- 

 maphrodite tree found in a Honolulu papaya orchard and producing fruit of 

 excellent flavor was grown to the second generation. Of 343 F2 trees old 

 enough to exhibit sex characters 94 per cent were fruit bearing. Although it 

 is considered probable that varied forms of flowers and fruits will appear it is 

 hoped that it will be possible to develop a pure strain of uniform shape. 



