306 Maine Agricultural Experiment Station. 1917. 



Net fertility, as measured by the reproductive index, is a 

 rather highly variable character, agreeing in this rfespect with 

 other purely physiological characters. 



Reproductive ability, as measured by the index, dimishes 

 with advancing age of the birds mated, having its maximum 

 when each of the birds mated is from lo to 14 months of age. 



The decline in reproductive ability with advancing age is 

 at a more rapid rate in the case of the males than in the case of 

 the females. 



STUDIES ON OAT BREEDING V. 



The El and F, Generations of a Cross Between a Naked 

 ' AND A Hulled Oat.* 



This paper is an account of the results obtained from a 

 cross between representatives of two subspecies Avena sativa 

 patula var. Victor and Avena sativa mtda var. inermis. The 

 contrasting characters involved in this cross are : firm flowering 

 glumes, biflorous spikelets, black color of the glumes, strong 

 awns, a long but sparse pubescence at the sides of the base of 

 the lower grain — vs. loose membranous flowering glumes, mul- 

 tiflorous spikelets, white or light yellow glume color, and almost 

 total absence of awns and the absence of pubescence. 



The El generation is distinctly intermediate in most char- 

 acters. In regard to the glumes, both naked and firml}^ hulled 

 grain as well as intermediate forms are found on the same 

 panicle and even in the same spikelet. 



The E2 generation segregates into a large number of inter- 

 mediate forms. In addition to the two parental hull types, four 

 intermediate classes were distinguished. These intermediate 

 forms contain all gradations from the plants with perfectly 

 hulled grain to the perfectly naked forms. 



The inheritance of the hull characters presents a simple 

 Mendelian relation giving i hulled, 2 intermediate, i naked. 

 Likewise, in respect to grain color, there are 3 plants with black 

 grain to i plant with white grain, the genes for these two char- 

 acters, segregating independently of each other. 



*This is an abstract from a paper by Jacob Zinn and Frank M. 

 Surface, having the same title and published in the Journal of Agri- 

 cultural Research Vol X, pp. 293-312. 



