212 THE SMALL GRAINS 



Dominant characters : Corresponding recessives : 



Keeled glumes Rounded glumes 



Hollow culms Solid culms 



Pubescent chaff Glabrous chaff 



Broad leaves Narrow leaves 



Hard kernels Soft kernels 



Rust liability Rust resistance 



Many of the above-mentioned dominants and recessives 

 were determined for wheat by Biffen (1905, pp. 23-48), 

 who began investigations in 1900, having in view the im- 

 provement of English-grown wheat. More recently 

 Thatcher (1913, pp. 37-50) has determined certain of 

 these characters for oats and barley, as follows : 



Dominants :. Recessives : 



Barley 



Hulled kernels Hulless kernels 



Hooded spikes Awned spikes 



Two-row spikes Six-row spikes 



Oats 



Black hull White hull 



Spreading panicle Side panicle 



222. Occurrences of aberrant forms. Many occur- 

 rences of strange forms in a field of grain, which have 

 been called reversions to ancestral characters or muta- 

 tions, are rather to be considered as new combinations of 

 existing units, as the result of natural crossing. Some 

 may also be outcropping recessives from intermediate 

 progeny remaining in selections from dominants in cases 

 of artificial hybrids; for it must be remembered that, 

 according to theory, the splitting of intermediates should 

 continue indefinitely. Some of these aberrant forms 

 that are most common are awned spikes in awnless wheat, 



