90 GENETICS [Bot. Absts. 



been model for repeated "mimic" mutations and has itself been "recurrent." Purple was 

 used most extensively in early analysis of autosomal linkage — coupling F 2 , back-cross test of 

 crossing over in both male and female, two-point map, three-point map, etc. Coincidence 

 curve for age-variation in crossing over is roughly mirror image of crossover curve for age- 

 variation, while coincidence curve for temperature-variation in crossing over seems to be 

 straight line independent of temperature curve of crossing over. Age and temperature varia- 

 tions in crossing over seem therefore to depend on two different physiological factors affecting 

 respectively "internode length" and "coefficient of crossing over." — Calvin B. Bridges. 



602. Bridges, Calvin B. Specific modifiers of eosin eye color in Drosophila melanogas- 

 ter. Jour. Exp. Zool. 28: 337-384. July 5, 1919— See Bot. Absts. 3, Entry 2092. 



603. Bridges, Calvin B. Vermilion-deficiency. Jour. Gen. Physiol. 1:645-656. July 

 20, 1919.— See Bot. Absts. 3, Entry 982. 



604. Brown, N. E. The defertilization of flowers by insects. Gard. Chron. 63: 4. 1918. 

 — Author observed a Syrphid fly eating the pollen from anther and stigma of a Pelargonium 

 flower. — John Bushnell. 



605. Coe, H. S. Origin of the Georgia and Alabama varieties of velvet bean. Jour. Amer. 

 Soc. Agron. 10: 175-179. 2 fig. 1918.— See Bot. Absts. 3, 1471. 



606. Collins, E. J. Sex segregation in the Bryophyta. Jour. Genetics 8: 139-146. PI. 

 6, 6 fig. June, 1919.— See Bot. Absts. 3, Entry 2103. 



607. Collins, G. N. Intolerance of maize to self-fertilization. Jour. Washington, D. C, 

 Acad. Sci. 9: 309-312. June 4, 1919. Of several hundred strains of maize (Zea) which have 

 been repeatedly self-fertilized only one has been discovered which does not suffer a loss of vigor 

 in consequence. — This intolerance of self-fertilization is difficult to reconcile with the flowering 

 habits of maize, most varieties of which are synacmic or slightly proterandrous. It is pointed 

 out that a slight departure from synacmy toward proterogyny would not only increase the 

 chances for cross-fertilization, but would also insure complete fertility when climatic condi- 

 tions were unfavorable for the distribution of pollen. — An explanation of the combination of 

 synacmy with an intolerance to self-fertilization is suggested by the idea of the hybrid origin 

 of this species. Euchlaena the nearest relative of maize and generally regarded as an ancestor 

 shows no measurable reduction of vigor as a result of self-fertilization. It must be assumed 

 therefore that the intolerance of self-fertilization is a character derived from some source 

 other than Euchlaena. It does not seem unreasonable to suppose that the ancestor possess- 

 ing this intolerance would have also some means of insuring cross fertilization. Perfect- 

 flowered spikelets and androgynous inflorescences of maize are proterogynous. The sexes, 

 however, are normally separated, the male inflorescence occupying a terminal and the female 

 inflorescence a lateral position on the plant. Terminal inflorescences mature before lateral 

 and the delay attendant on a lateral position neutralizes the natural proterogyny. The con- 

 clusion is reached that the unknown ancestor of maize was perfect-flowered and was protected 

 from self-fertilization by complete proterogyny. While maize retains the intolerance of self- 

 fertilization of this perfect-flowered, proterogynous ancestor the protective proterogyny is 

 lost through the separation of the sexes, a characteristic derived from Euchlaena. — J. H. 

 Kempton. 



608. Connors, C. H. Methods in breeding peaches. Proc. Amer. Soc. Hortic. Sci. 14 

 (1917) : 126-127. 1918. — Early attempts in trying to cross peaches when paper bags were used, 

 proved practically negative. Mosquito netting shows slightly better results, but not entirely 

 satisfactory. Later attempts were made to enclose entire tree with cheese cloth supported on 

 framework, with quite satisfactory results. — Object was to study inheritance of size of blos- 

 soms. It was first thought that size of blossom might be due to hybridization, but is now 

 known that all sizes are found in the wild forms in China. Crosses and selfings were made. 



