Abstracts. 307 



Multiflorous spikelets occvir only in connection with naked 

 grain. Plants with completely hulled grain bear only biflorous 

 spikelets. 



The inheritance of the pubescence at the base of the lower 

 grain presents some difficulties, since this character can not 

 manifest itself on plants with naked grains. In the group of 

 plants having hulled and intermediately hulled grains the pu- 

 bescence behaves as a bifactorial character, giving 15 pubescent 

 plants to 1 without pubescence. Neither of these genes are 

 linked with the color genes. 



The long and short pubescence at the base of the grain be- 

 haves as a monohybrid character and segregates independently 

 of the other genes considered. 



An interesting feature of this cross is the presence of pu- 

 bescence at the base of the upper or second grain. No cultivated 

 oat varieties possess this character. In this cross these forms 

 occur only on spikelets where the lower grain is naked or semi- 

 naked, indicating that this condition may be due to physiological 

 disturbances caused by the presence of the naked lower grain. 



In regard to the inheritance of the awn character, the hulled 

 and intermediately hulled types of grain appear to present a 

 'simple 3 to I ratio between plants with medium strong to strong 

 awns and those plants with weak awns. 



STUDIES ON INBREEDING. VII. 



Some Furth-er Consideration Regarding the Measurement 

 AND Numerical Expression of Degrees of Kinship.* 



This paper has as its object the defining in simple manner 

 the basic concepts of inbreeding. On the basis of these defini- 

 tions a new and more accurate method of measuring and ex- 

 pressing numerically the degree of kinship between any two 

 individuals, whatsoever, whose pedigrees are known, is possible. 

 This new constant, the partial inbreeding index, is defined as 

 the part of the total inbreeding exhibited in the pedigree of any 

 individual which is due to relationship between the sire and 

 the dam of that individual. 



*This paper is an abstract from a paper bj^ Raymond Pearl, having 

 the same title and published in The American Naturalist, Vol. LI, No. 

 609, pp. 545-549. 



