27 o THE WHEAT PLANT 



T. dicoccoides or T. dicoccum with one or two species ofAegilops (see Chapter 



XXIII.). 



The natural classification and description of such a series presents 

 much the same problems and a similar degree of complexity as the classi- 

 fication of the human race, and nothing less than a minute description of 

 individuals would adequately represent it. 



The artificial classification into varieties presents 

 no difficulty, and a few common forms of each 

 variety are described later. 



Some broadly outlined natural groups are readily 

 recognised when the living plants are studied, 

 although the lines of demarcation are in some cases 

 obliterated by the normal fluctuating variations 

 of the different forms composing them. Among 

 such groups of apparently genetically related forms 

 are the following : 



GROUP I. The endemic forms of T. vulgar c 

 from India and also several from Persia and 

 Turkestan. These are all early, rapid-growing 

 forms, which come into ear at Reading about the 

 end of May or first week in June when sown in 

 autumn or early spring ; under favourable climatic 

 conditions many of them are able to produce ripe 

 grain in one hundred days or less from the time of 

 sowing. 



The young shoots are erect, straw slender, in- 

 clined to curve towards the ground, in cool seasons 

 short, 76-90 cm. (30-36 inches) high, in hotter 

 years taller, leaves yellowish-green in the early, and 

 more or less glaucous in the later forms. 



The ears are often quadrate, short, or of 



FIG. 168. Grains of the medium length, from 6 to 10 cm. long, usually 

 spikelets of one side of lax and rigid, with a somewhat brittle rachis. The 

 ?r.%.?5ri5 density of " pedigree " lines in this group is more 

 variable than in any other, especially when com- 

 parison is made between plants sown in autumn and those of the 

 same line sown in spring. 



The spikelets, 12-20, are sometimes arranged irregularly on the rachis, 

 especially in the case of lax ears ; in the denser ears they overlap each 

 other. 



The empty glumes are rigid, scabrid, and not infrequently keeled to 

 near the base ; in the bearded forms the awns of the flowering glumes are 

 short (4-6 cm. long), scabrid, brittle, and divergent. 



