No. 1, November, 1921] GENETICS 11 



74. Blakeslee, a. F. The Globe mutant in the jimson weed (Datura Stramonium). 

 Genetics 6: 241-2G4. 1921. — The Globe mutant is distinguished as a seedling by its broad 

 entire first leaves. In the first leaves of 98 Globes, length divided by breadth averaged 1.5; 

 while in 98 normal sibs of these Globes it averaged 2.1. Globe plants have more closely over- 

 lapping and broader leaves, which are less toothed; the capsules are depressed globose, and 

 have stouter spines. Globe seedlings are less vigorous than normals. Globes selfed gave 

 4403 Globes to 1G,075 normals, a percentage of 21.5. Globes pollinated by normals gave 917 

 Globes to 2351 normals, or 28.1 per cent of Globes. Normals crossed by Globe pollen gave 

 57 Globes to 3302 normals, or only 1 .7 per cent of Globes. Normal sibs of Globes selfed pro- 

 duced only 4 Globes to 2072 normals, or 0.2 per cent. In other normal lines 24 apparently 

 original Globe mutations were found, together with 38, 108 normal plants, which is a percentage 

 of 0.06. However, one line extensively grown gave a disproportionately large number of these 

 Globes. The other 11 mutants of Datura selfed gave 0.2 per cent of Globes, and when crossed 

 by normal pollen, 0.3 per cent; while normals crossed by pollen of these mutants gave 0.1 

 per cent. — Nineteen normal plants gave an average of 2.7 per cent of bad pollen, while 7 Globes 

 at the same time averaged 7.9 per cent, over 1000 grains being counted from each plant. Other 

 extensive pollen counts gave similar results. — Selection for 10 generations failed to increase 

 the number of Globes in the progeny. — The Globes show 12 and 13 chromosomes in the pollen 

 mother-cells after the reduction division. It is presmned that the pollen grains with 13 chro- 

 mosomes rarely function, and either that some of the 13-chromosome egg cells do not func- 

 tion, or that the 25-chromosome zygotes are less viable than the 24-chromosome zygotes 

 in the early stages. — John Belling. 



75. Blaringhem, L. Sur le pollen dulinet la degenerescence des varietes cultivees pour la 

 fibre. [On the pollen of flax and the degeneration of varieties cultivated for fiber.] Compt. 

 Rend. Acad. Sci. Paris 172: 1603-1604, 1921.— The degeneration of flax is considered to be 

 due to genetic rather than climatic influences. Hybrids between different cultivated annual 

 flaxes and the wild biennial L. angustifolium are fertile but give pollen some of which is par- 

 tially aborted. The large pollen grains are variable in size and shape. All the annual flaxes 

 cultivated for grain are early-maturing, homogeneous in type, and give perfect, uniform pollen. 

 Most of the fiber flaxes are heterogeneous in type, and their pollen is irregular or a small 

 proportion is even aborted; these facts make it possible to suppose that these flaxes have had 

 a remote hybrid ancestry. One strain of fiber flax of Russian origin was found to be uniform, 

 early, well fixed in type, and to have perfect and very regular pollen. The selection of fiber 

 flaxes based on a study of the pollen of isolated strains continued through several successive 

 generations is recommended as a procedure for avoiding degeneration of the common varie- 

 ties. — D. F. Jones. 



76. Bridges, C. B. Proof of non-disjunction for the fourth chromosome of Drosophila 

 melanogaster. Science 53: 308. 1921.— The author states that he secured genetic evidence 

 of non-disjunction of the 4th chromosome in Drosophila melanogaster during the summer of 

 1920 and obtained cytological verification later the same year. He then shows that the genetic 

 evidence recently given by Little (Science 53 : 167. 1921) is susceptible of interpretation as 

 due either to the presence of a new, less extreme eyeless allelomorph, or to a dominant 4th- 

 chromosome minus modifying factor, as well as to non-disjunction. — H. H. Plough. 



77. Bridges, Calvin B. White ocelli— an example of a "slight" mutant character with 

 normal viability. Biol. Bull. 38: 231-236. 1920.— A description and genetic data of a mutation 

 in D. melanogaster in which the ocelli or simple eyes are white instead of the normal browa 

 color are given. The gene producing this effect is located in the 3rd chromosome between> 

 hairless and rough. The mutation is very slightly different from the normal, though definite 

 and easily distinguished. It causes no diminished viability and actually persisted in mixed 

 mass cultures for fully 175 generations without selection. Such a mutant might survive in 

 nature, and if slightly advantageous might supplant the original type. — H. H. Plough. 



