38 GENETICS [BoT. Absts., Vol. VII, 



239. ScHRADER, Franz. Sex determination in the white-fly (Trialeurodes vaporariorum). 

 Jour. Morph. 34: 267-305. 4 V^- Sept. 20, 1920. — Other workers had discovered that virgin 

 females of this white-fly produce only males in America, but only females in England. 

 Author shows that ,number of chromosomes in American race is 22 except in pseudo-vitelline 

 or mycetoma cells, where number is 30 or more. In female, maturation includes two divi- 

 sions, and mature egg contains eleven chromosomes. If egg is unfertilized, it produces male 

 with eleven chromosomes. In spermatogenesis reduction division is completely suppressed 

 and spermatozoa have haploid number of chromosomes. Whether egg is fertilized or not is 

 in some way controlled in female. — Author suggests parthenogenetic production of females 

 (as in England) may be due to reunion of polar nucleus with egg nucleus, or to doubling of 

 number of chromosomes at some stage. If fertilized eggs of English race produce both 

 sexes, explanation may be that entrance of spermatozoon causes reduction of chromosomes 

 in egg (a process omitted or neutralized in parthenogenetic egg), but some of spermatozoa 

 do not function any further, leaving egg to develop with haploid number and produce male. — 

 English race is supposed to have originated from American, perhaps by mutation. Occur- 

 rence of some males in England may be result of importation from America. — A. Franklin 

 Shull. 



240. Shamel, a. D., L. B. Scott, C. S. Pomeroy, and C. L. Dyer. Citrus-fruit improve- 

 ment: a study of bud variation in the Eureka lemon. U. S. Dept. Agric. Bull. 813. 88 p. 

 18 tables, 22 fig. June, 1920. — The methods employed in this investigation have been, in 

 general, like those used in the three previously reported studies of orange and grapefruit 

 varieties (see Bot. Absts. 2, Entries 707, 708, 709). Selected plots in Eureka lemon orchards 

 including 252 trees altogether, have furnished detailed records of yield, grade, etc., while 

 cooperative arrangements have given individual records for about 14,000 trees. Extensive 

 statistical data, covering about 6 years (1911-1917) are presented. — Eight strains of Eureka 

 lemon are described, all of which "have been traced to individual fruit or limb variations in 

 trees growing under normal conditions," and have been experimentally propagated by 

 budding. These strains differ in many characters, such as habit of growth, size and shape 

 of leaves, productiveness, shape of fruit, thickness of rind, and season of production. The 

 Eureka strain, which is that most typical of the variety as usually grown, is the only type desir- 

 able for commercial lemon production. Trees of certain other types, such as the Shade- 

 tree strain, are numerous in some orchards, evidently because of the former practice of 

 using as budwood the vigorous non-bearing shoots, which are especially numerous with these 

 strains. — The authors advise that all buds for propagation be taken from shoots bearing 

 normal fruits, and that these bud sticks be cut only from superior performance-record trees; 

 also, that orchard trees of inferior strains be top-worked or replaced. — Howard B. Frost. 



241. Shamel, A. D., L. B. Scott, C. S. Pomeroy, and C. L. Dyer. Citrus-fruit improve- 

 ment: a study of bud variation in the Lisbon lemon. U. S. Dept. Agric. Bull. 815. 70 p., IS 

 tables, 14 fi^. June, 1920. — The work with the Lisbon lemon closely paralleled that with the 

 Eureka lemon (see Bot. Absts. 7, Entry 240) in methods, general results, and conclusions. 

 Detailed records were secured for 128 trees in selected plots, and cooperative records for 

 about 13,000 trees. Five definite strains are described in detail; others have been observed 

 but not thoroughly studied. Of these five strains, the Lisbon strain, representing "the 

 established ideal for the Lisbon variety," is the most productive. The Open strain, though 

 less hardy and productive, has an advantage in its tendency to produce fruit throughout the 

 year, resembling the Eureka strain of the Eureka variety in this respect. In some orchards 

 the Open strain predominates, and in others the Lisbon strain. The other strains are mark- 

 edly inferior. — Howard B. Frost. 



242. Stark, Mary B. A benign tumor that is hereditary in Drosophila. Proc. Nation. 

 Acad. Sci. [U. S.] 5: 573-580. 5 fig. Dec, 1919.— A new benign tumor appeared in a stock 

 of Drosophila. By inbreeding, a strain true to the tumor character was established. One 

 gene for the tumor is situated in the third chromosome close to dichaete. Extraction of the 



