Aug. 6, 19 1 7 



Stvdies on Oat Breeding 



309 



of that pubescence is controlled by the pubescence of the lower grain and, 

 as Surface (6) showed for the cross between wild and cultivated oats — 



in the absence of the gene for pubescence on the lower grain the gene for pubesence 

 on the upper is unable to act. 



D. — INHERITANCK OF AWNS 



The inheritance of the awn character remains to be discussed. The 

 behavior of this character, like the pubescence discussed above, is closely 

 associated with the morphological constitution of the lower flowering 

 glumes and is affected by the same disturbances caused by the naked 

 parent. As already stated, the strength of the lower flowering glume in 

 the intermediate forms may vary on the same panicle, or even whorl, 

 from a thin membraneous condition to the coarseness and strength of the 

 normal hull. These variations of the glume are accompanied by cor- 

 responding variations in the strength of the awn. The naked forms and 

 the naked spikelets of the intermediate forms bear only a very weak, 

 thin awn, often appearing as a tender prolongation of the median, 

 vascular bundle at or near the tip of the glume. The group of inter- 

 mediate forms approaching the firmly hulled forms have partly a weak 

 awn and partly a medium strong awn, with a distinct twisted, basal 

 portion. The third group, including only plants with firmly hulled 

 grain, possesses a strong kneed and twisted awn along with medium 

 strong awns. Table IX shows these three groups of plants in relation 

 to the three classes of awns. 



Table IX. — Relation of the hull character to the strength of the awn 



The relation between the kind of awn and character of hull is very 

 evident. In the naked and seminaked group practically all awns are 

 weak. In the middle group approaching the firml}' hulled type of grain, 

 the weak awns on one hand and the medium and strong awns on the 

 other occur in approximately equal numbers. In the third class a con- 

 dition opposite to that of the first group is reached, where 88 per cent 

 of the plants have medium strong and strong awns. It may be stated 

 that the same tendency also prevails in regard to the quantitative dis- 

 tribution of the awns, the lowest number of awned spikelets being corre- 

 lated with the weakest kind of awn and, conversely, plants with strong 

 awns having usually all spikelets awned. 



