CLASSIFICATION AND INHERITANCE OF SMALL GRAINS 105 



standard awned strains. Likewise, many hooded hybrids have 

 been produced but none has proved satisfactory. The facts 

 lead to the conclusion that "the awn is an organ that is func- 

 tional under most conditions, and especially in those sections 

 where humid weather prevails, at ripening time." A study of the 

 effect of the removal of the awns on the development of the seeds 

 of the spike showed that spikes with awns removed (clipped 

 spikes) produce a lower weight of dry matter at maturity than 

 normal spikes. As the seeds develop as rapidly for several days, 

 after the awn is removed, in clipped spikes as in undipped, the 

 difference in development at maturity is not due to the shock of 

 removing the awns. About one week after flowering, the deposit 

 of dry matter in the normal spikes begins to exceed that in the 

 clipped spikes. This is stated to be at the time rapid starch 

 infiltration begins. Normal spikes at maturity, near Aberdeen, 

 Idaho, have a content of more than 30 per cent, of ash in the 

 awns. The rachises of the clipped spikes at maturity contained 

 about 25 per cent, more ash than those of normal spikes, which 

 probably accounts for the greater tendency of clipped spikes to 

 break. 



These facts show that under humid conditions there is a 

 physiological reason why awned varieties yield higher than 

 hooded or awnless varieties. They are given as an illustration 

 of the value to the plant breeder of a knowledge of the physiolog- 

 ical functions of the various organs of plants. 



Two methods of attack are outlined for the barley breeder: 

 (1) The use of varieties which normally have a low percentage of 

 ash in the rachis might make possible the production of non- 

 shattering hooded and awnless sorts. (2) The production of 

 smooth-awned varieties, which in a large measure, would over- 

 come the objection to the barley awn. 



The production of high-yielding smooth-awned varieties is not 

 a difficult task, as has been learned by cooperative studies carried 

 on at the Minnesota Station. As smooth awn is a recessive 

 character, all that is necessary is to cross high-yielding toothed 

 varieties with smooth-awned sorts, and then select smooth- 

 awned plants in F 2 . These will breed true for the smooth-awned 

 character. Numerous plants should be selected, as some will 

 prove more valuable than others for economic characters such 

 as yield, non-shattering habit, and stiffness of straw. 



