Varietäten, Descendenz, Hybriden. 229 



The Fj and F2 Generations of a cross between a naked 

 and a huUed oat. (Journ. agric. Research. X. p. 293—312. 

 Washington, 1917.) 



The present paper contains a description of the F^ and Fg 

 generations of a cross between a black hulled oat, Avena sativa 

 patula var. Victor, and a white naked oat, Avena sativa nuda 

 var. inermis. 



The hulled parent is characterized by the presence of firm 

 flowering glunies (paleae) which adhere closely to the caryopsis, 

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

 a long but rather sparse pubescence at the sides of the base of 

 the lower grain. 



The naked parent is characterised by the presence of loose 

 membranous flowering glunies which do not adhere to the cary- 

 opsis, multiflorous spikelets, white or light yellow glume color, 

 almost total absence of awns and the absence of pubescence. It 

 is possible that the absence of awns and of pubescence is due to 

 the inability of these characters to express themselves on the thin 

 membranous glumes. 



The F^-generation is distinctly intermediate in most characters. 

 In regard to the glumes, both naked and firmly hulled grain as 

 well as intermediate forms are found on the same panicle and 

 even in the same spikelet. As the writer shows in a table, the 

 spikelets near the top of the panicle are either entirely naked or 

 nearly so, while those spikelets near the base of the panicle tend 

 to be firmly hulled. A similar but less marked relation is to be 

 observed between the spikelets at the tip and base of each whorl. 



In the Fg-generation a large number of intermediate forms 

 appear. In addition to the two parental huU types, four interme- 

 diate classes were distinguished. These intermediate forms contain 

 all gradations from the plants with perfectly hulled grains to the 

 perfectly naked forms. 



In another table is shown the inheritance of the huU characters 

 presenting a simple Mendelian relation giving 1 hulled, 2 inter- 

 mediate, 1 naked. Likewise, in respect to grain color, there are 

 3 black plants to 1 white in the second generation. Two other 

 tables show the genes for these two characters separating indepen- 

 dently of each other. 



In all cases multiflorous spikelets occur 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 som^e difficulties since this character can not mani- 

 fest itself on plants with naked grain. By using a selected group 

 of plants having hulled and intermediate grain it is found that 

 this pubescence behaves as a bifactorial character, giving 15 

 pubescent plants to 1 without pubescence. Neither of these genes 

 are linked with the color genes. 



The evidence available indicates that one of these pubescent 

 genes may come from the naked parent. 



The presence of long and short pubescence at the base of the 

 grain behaves as a monohybrid character and segregates indepen- 

 dently of the other genes considered. 



A remarkable feature of this cross is the presence of pubes- 

 cence at the base of the upper or second grain. There are no 

 cultivated varieties of oats which possess this character. In the 



