36 GENETICS [BoT. Absts., Vol. VIII, 



show a proportional reduction of both chlorophyll and the yellow pigments. Xantha shows a 

 slight increase of yellow with a large decrease of the green. Xantha survives only when 

 grafted on green plants, when it sets seed. Various crosses were made with typica, xantha, 

 and chlorina. The results are explicable on the assumptions: (1) That xantha possesses the 

 factors ZZ for yellow pigments, (2) that chlorina has the formula ZZCCnn, and (3) that 

 typica is N NCCZZ, where N is operative only when C is present. Four green genotypes, 

 phenotypically alike, were identified as follows: (1) A type which when selfed gives 3 green to 

 1 chlorina, (2) a type which jaelds 9 typica: 3 chlorina: 4 xantha, (3) a type producing 3 typica: 

 1 xantha, and (4) homozygous typica. Typica X chlorina heterozygotes are only about 90 

 per cent as green as typica but heterozygotes of typica or chlorina with xantha are indistin- 

 guishable from the respective green homozygotes. Urtica urens peraurea is a yellow form 

 which increases in green with age and is able to live independently. On account of its defi- 

 ciency in chlorophyll it does not grow so rapidly nor to so great a size as the species. Selfing 

 shows it to be a monohybrid which yields 2 greens to 1 peraurea. Satisfactory evidence has 

 been secured to show that the 2:1 ratio arises through the failure of the yellow homozygote 

 to live. A discussion is presented of the ratios to be expected in monohybrids when there is 

 selective union of gametes, deficiency or excess of pollen, or inviable zygotic combinations. — 

 Leonas L. Burliyigame. 



245. Coulter, Merle C. Origin of mechanism of heredity. Bot. Gaz. 70: 459-464. 

 1920. — Author attempts to account for the evolutionary origin of the determiners (genes). 

 He thinks they originated as by-products of metabolism. These by-products, he supposes, 

 became isolated by anti-bodies and in later generations were released and induced the same 

 kind of chemical changes as those of which they were the by-products. — Edgar Altenburg. 



246. Crocker, Wm. Awn and barley yield. [Rev. of: Harlan, H. V., and S. Anthony. 

 Development of barley kernels in normal and clipped spikes and the limitations of awnless and 

 hooded varieties. Jour. Agric. Res. 19 : 431-472. 1920. (See Bot. Absts. 6, Entry 1416.) ] Bot. 

 Gaz. 71:77-78. 1921. 



247. Daniel, Lucien. Obtention d'une race nouvelle d'Asphodele par I'action du climat 

 marin. [The appearance of a new variety of Asphodelus through the eflfect of a marine climate.] 

 Compt. Rend. Acad. Sci. Paris 170: 1332-1333. 1920. — Asphodelus luteus originally obtained 

 from Rennes has become remarkably modified after 20 years at Erquy. New form divided 

 vegetatively and taken back to Rennes retained its acquired characters in full. Parallel 

 sowings of seed of two forms reproduced differences exhibited by parents. Experiments are 

 being continued. Author considers observations particularly significant for question of 

 inheritance of acquired characters. — R. E. Clausen. 



248. Dehorne, Armand. Spermatogenese de Corethra plumicornis et chromosomes 

 eupyrenes. [Spermatogenesis of Corethra plumicornis and eupyrene chromosomes.] Compt. 

 Rend. Acad. Sci. Paris 171 : 1399-1402. 1920. 



249. Desmoulins, A., et V. Villard. The hybrid direct bearers in the valley of the 

 Drome in 1919. Prog. Agric. et Vitic. (Ed. I'Est-Centre) 72: 62-65, 83-85, 114-116, 133-137. 

 1920. 



250. Detlefsen, J. A. Genetic analysis of low crossover stock produced by selection. 

 [Abstract.] Anat. Rec. 20: 211. 1921. — Following selection for low crossover values in red- 

 eyed long-winged females (Drosophila melanog aster) heterozygous in white miniature, a stock 

 was produced which has given crossover values of about 4-6 per cent for these 2 genes. The 

 normal value used in plotting chromosome maps is 33 per cent. Matings of red long females 

 from low crossover stock to white miniature males of normal stock gave Fi females which 

 show an intermediate value. When the Fi sibs were mated inter se, the total F2 results also 

 showed an intermediate crossover value. However there was a distinct increase in the range 

 of values. — Matings of red long males from low-crossover stock to eosin miniature females of 

 normal stock gave similar results. — J. A. Detlefsen. 



