Belling: A Study of Semi-Sterility 



73 



experiment extended over nearly seven 

 acres; in 1912, there were three acres; 

 and in 1913 over two acres of in- 

 dividually numbered plants, and several 

 acres of different families, were grown. 

 The results given here are based on an 

 individual study of over 2000 of these 

 plants, grown eight feet apart, and 

 (except in 1910) on eight-foot or four- 

 foot poles. 



These plants are favorable for an 

 investigation of semi-sterility since no 

 complications arise from self -sterility, 

 incompatibility, or intercrossing by 

 insects. Also the dry pollen is easily 

 squeezed in a mass from the closed 

 keel, and the seeds and aborted ovules 

 can readily be counted in the dry pods 

 as well as in the green pods. (Data 

 with regard to one complication due to 

 imperfect self-pollination and too short 

 style will be given in a forth-coming 

 paper) . 



The random abortion of half the 

 pollen-grains and half the embryo-sacs, 

 and the splitting of the progeny of the 

 semi-sterile plants into half semi-sterile 

 and half fertile, as well as the constancy 

 of the fertile plants, agree in all details 

 with a simple Mendelian hypothesis, in 

 which the pollen-grains and embryo-sacs, 

 not the zygotes, are the individuals 

 affected by segregation. If the Velvet 

 bean has a factor whose absence stops 

 the development of those pollen-grains 

 and embryo-sacs which lack it, and the 

 other three allied beans have another 

 similar factor segregating independently, 

 then those pollen-grains and embryo- 

 sacs of the hybrid which have both 

 factors will be abnormal, because 

 unlike the zygote, they normally have 

 single and not double factors. Hence 

 those pollen-grains and embryo-sacs 



which lack both factors, and those 

 which possess both factors, alike fail 

 to develop. This hypothesis can be 

 verified or disproved by appropriate 

 crosses between different fertile hnes, 

 which I hope to undertake. 



THE POINTS OF INTEREST. 



The following are noteworthy points : 



(1) Accurate knowledge of the exact 

 degree of sterility of some hybrid 

 plants can be obtained by microscopical 

 examination of the pollen of healthy 

 flowers, and of microtome sections of 

 the ovules. 



(2) The explanation of the random 

 abortion of half the pollen-grains and 

 half the embryo-sacs must apparently 

 be by the segregation of Mendehan 

 factors among these individually, and 

 not by the action of these factors on the 

 zygotes. 



(3) Semi-sterility resulting from cross- 

 ing is apparently one of the simplest 

 cases of sterility, and a knowledge of its 

 inheritance may help in the investiga- 

 tion of the probably more complicated 

 inheritance of the greater degrees of 

 sterility found in many first-generation 

 hybrids. 



I wish to thank the Plant Physiologist 

 of this Station, B. F. Floyd, for verifying 

 my numerical results by an independent 

 examination of the pollen-grains and 

 the series of sections of ovaries of the 

 hybrid (Velvet by China) ; and also 

 C. D. Gunn, and C. W. Long, who 

 have done much careful work, especially 

 in counting seeds and examining flowers. 



Note. I will send seeds of semi- 

 sterile plants to any member of the 

 American Genetic Association who may 

 require them. 



Neglected Opportunities 



If a tenth part of the labor and cost now devoted by leisured persons, in this 

 country alone, to the collection and maintenance of species of animals and plants 

 which have been collected a hundred times before, were applied to statistical 

 experiments in heredity, the result in a few years would make a revolution not 

 only in the industrial art of the breeder, but in our views of heredity, species 

 and variation.— William Bateson: Mendel's Principles of Heredity (1902). 



A report from Berne, Switzerland, states that the Swiss Society of Public 

 Utility for Women has established a biireau for the medical examination and 

 certification of women for matrimony. 



