No. 1, May, 1921] GENETICS • 35 



242. CoRRENS, C. Die Konkurrenz der mannlichen und die weiblichen Keimzellen und 

 das Zahlenverhaltnis der beiden Geschlechter. [The concurrence of male and female germ- 

 cells and the numerical relations of the two sexes.] Naturwissenschaften 6: 277-280. 1918. — 

 The dioecious plant, Melandrium, when pollinated with a small amount of pollen gave a ratio 

 of 737 pistillate to 555 staminate plants, and when a large amount of pollen was applied gave 

 a ratio of 895 pistillate to 381 staminate. In the first case there were 43 per cent and in the 

 second 30 per cent of staminate plants, showing that when the competition is keen the stami- 

 nate-determining pollen nuclei are at a greater disadvantage, due to a slower growth of the 

 pollen tubes carrying them. When the pollen is not in excess the slower-growing tubes have 

 a better opportunity to fertilize, but even in those cases the sex ratio is not equal, a larger 

 number of pistillate plants always resulting. — D. F. Jones. 



243. CoRRENS, C. Fortsetzung der Versuche zur experimentellen Verschiebung des 

 Geschlechtsverhaltnisses. [Continuation of experiments to shift the sex-ratio experimentally.] 

 Sitzungsber. Preuss. Akad. Wiss. Berlin 1: 1175-1200. S fig. 1918. — InMelandrium there are 

 ordinarily more female plants than male. The object of these experiments was to find means 

 to alter the sex-ratio and thereby discover its determining factors. The method employed 

 was that of varying the amount of pollen used in pollinations. There are about 350 ovules 

 in an average capsule. When the amount of pollen applied is only slightly in excess of this 

 number the resulting progeny shows an approximate equality of sexes (about 44 per cent 

 males), but when a large excess (60,000 grains) is applied the proportion of males falls to about 

 32 per cent. This difference is about 8 times the probable error. The inference made is that 

 there are two kinds of pollen — male-determining and female-determining — and that the sec- 

 ond sort produces more active pollen tubes, which reach the ovules in advance of those of the 

 male-determining sort. If a minimal amount of pollen is employed the female-producing 

 tubes arrive first at the upper ovules and fertilize them leaving the slower male-determining 

 ones to the lower ovules. Separating the seeds in the capsule into a lower and an upper 

 portion confirmed this hypothesis by showing an excess of female plants from the upper seeds. 

 It was also shown that female plants mature more quickly than males so that the propor- 

 tion of males the first season was slightly lower than among the plants which lived over the 

 winter and flowered the next season. Some experiments were also made showing that there 

 is a differential mortality among pollen grains dried over sulphuric acid for 10 to 14 days. The 

 male-determining appear to be weaker. Some apparently good seeds are always found incapa- 

 ble of further growth. Among seeds produced from old pollen this proportion is much larger, 

 and in fact many of the embryos and ovules do not mature to the seed stage, dying at various 

 stages. — Leonas L. Burlingame. 



244. CoRRExs, C. Zur Kenntnis einfacher mendelnder Bastarde. I. Die Unterscheidung 

 der pilulifera-Homozygoten und der Heterozygoten des Bastardes Urtica pilulifera X Dodartii. 

 II. Mirabilis jalapa xantha und ihre Bastarde. III. Urtica urens peraurea. [A contribution 

 to the knowledge of simple Mendelian hybrids. I. Distinguishing the homozygote from the het- 

 erozygote of Urtica pilulifera X Dodartii. II. Mirabilis jalapa xantha and its hybrids. III. 

 Urtica urens peraurea.] Sitzungsber. Preuss. Akad. Wiss. Berlin 1 : 221-268. 1918.— Although 

 the adult pilulifera homozygote and the hybrid are indistinguishable, as are also the cotyledon 

 stages of the seedlings, yet the young plants can be distinguished by the character of the 

 apices of the first 3 or 4 pairs of leaves. The tips of these first leaves show dominance of the 

 Dodartii parent but in the later leaves the pilulifera parent appears to be completely domi- 

 nant. As an explanation it is suggested that the Dodartii factor D becomes active earlier in 

 ontogeny than the factor P which pilulifera has in addition to D, that is, D expresses itself 

 only until P becomes active. — The xantha form of Mirabilis jalapa has only about 5 per cent 

 as much chlorophyll as the normal (typica) form. Chlorina has about 30 per cent and semi- 

 chlorina about 60 per cent of tijpica. Variegata has ground color of chlorina with full green 

 flecks superposed. Albomaculata has leaves with white and green streaks and flecks. The 

 amount of pigments was determined by comparison of crude alcoholic extracts of the same leaf 

 area in some cases and of the same weight of leaves in others. Chlorina and semichlorina 



