Sammelreferat. 145 



from nuda crosses and consequently set 4 or ö grains per spikelet. Of course, 

 too much weight must not be given to ex parte statements of seed cata- 

 logues: at least in the case of two new such varieties, recently much ad- 

 vertised, it is doubtful if they set 4 or 5 grains at all regularly, and in 

 any case, the extra grains are too small to be of commercial value. 



Both Caporn and Surface found that the F, from nuda X Mtiia give plants 

 on which the panicles contain both tight and loose grains, and in which 

 the paleae show every degree of interfascicular sclerosis. The F, showed 

 a bewildering mixture of plants from one parental form to the other. How- 

 ever the plants in which all the grains were tight seemed to bear a good 

 3:1 ratio to the remaining mixed types, and an Fj generation confirmed 

 this view (1) and (10). As regards the various intermediate forms, Caporn 

 tentatively put forward a 3 factor hypothesis: namely X, a factor which 

 makes all the paleae on the plant tight; Y, a factor which renders some 

 of the paleae on the plant tight: and Z, a factor which renders some of 

 the paleae on the plant sclerotised, but never wholly tight (1). 



The most interesting fact which emerges from the nuda X sativa crosses 

 is that the multiflorous condition of the spikelet only appears in so far as 

 the grains are naked. The spikelet containing many grains of the saliva 

 type does not appear — the many flowered spikelet seems to be a function 

 of the membranous paleae. In nuda forms the spikelet with (J — 10 flowers 

 is found throughout the panicle. As soon as tight grains appear the multi- 

 flority is partially suppressed, and when completely tight spikelets extracted 

 in F, are considered, the maximum number of florets is four and that only 

 rarely, nor does this character reappear Avith any regularity in subsequent 

 generations (1). 



Resistance to Rust. 



There are only two records of experiments on the inheritance of resi- 

 stance to rust, Pwcinnia graminis acenae. and both of these are mere preli- 

 minary notes. One author finds resistance to be dominant, and the other 

 finds it to be recessive: one claims that the segregation is sharp and the 

 other that it is a case of continuous grading. Neither grew the material 

 to an F3 stage and one author omitted to record the F, and states that 

 his resistant parent was not pure for resistance (1^) and (cS). Evidently there 

 is here a field of research for workers more concerned with accurate data 

 than preliminary publication. 



It seems clear, then, that a good start has been made with recording 

 the genetics of the ordinary morphological characters of Avena. Except in 

 the case of the nurfa , crosses , the economic side of oats has hardly been 

 taken in hand by the scientist. Resistance to disease, quality of grain, and, 

 above all the extremely complex problem of yield, still wait for elucidation 

 at the hands of the scientific breeder. 



Indaktive AbstAmman^s- und Vererbung«lehri'. XXVII. JO 



