34 BULLETIN 137, U. S. DEPARTMENT OF AGRICULTURE. 



which each awn was marked with two parallel stripes of red extend- 

 ing from its base to its tip, and other spikes in which the same stripes 

 were deep purple. When examined in the laboratory, the color 

 proved to be two bright-red stripes in the epidermis, below which 

 were two chlorophyll-bearing parenchyma areas running the full 

 length of the awn. As long as the chlorophyll was present the color 

 effect was deep purple, but as soon as this disappeared it was light 

 red. 



SUMMARY. 



While all lesser distinctions must be based upon the broader- 

 groups and no study of a cereal can omit its classification, the plant 

 characters useful in taxonomic work and the ones most useful in 

 plant breeding are far from being the same. Plant breeding is con- 

 cerned with minute differences. The broad taxonomic divisions are 

 serviceable only as groups. The problem of the nursery is not to 

 separate a 6-rowed Manchuria from a 2-rowed Hanna barley, but 

 to detect a variant in a plat of Manchuria. 



Strains are often shown to be distinct in early growth by their rate 

 of development. All barleys rush through the early stages very 

 rapidly, and a selection that is one or two days earlier than a second 

 is very dissimilar in appearance on a given date. 



Leaf production is, in some ways, a varietal character. In some 

 varieties the third leaf appears in three days after the second, while 

 in others it occurs six days later. In the production of the fourth 

 leaf even a greater range exists. 



In some strains the first tiller appears decidedly later than the 

 fourth leaf. In others it appears earlier. In some the tillers are 

 all produced within a short time; in others the process is extended 

 over several days. 



The emergence of the awn is an extremely important note, as it 

 occurs at a time in the life of the plant when such an observation is 

 of great value. The development is usually normal at this time, as 

 hot weather and drought have ordinarily not yet had any effect. 

 The emergence of the awn has been found to be far more accurate 

 and more easily obtained than the date of heading. The precocity 

 of the strain at the time of the emergence of the awn is a heritable 

 character. 



The date of ripening is, unfortunately, often influenced by season 

 and, while a A T aluable character, is less dependable than the emergence 

 of the awns. 



A comparison of the development during all stages serves to reveal 

 many differences not apparent when each stage is taken separately. 



The length of the culm is of use as a local breeding note, but the 

 variations are not parallel when strains are planted in totally dif- 



