CLASSIFICATION 161 



I find that the ear-density of some forms of Bread Wheat from India 

 and Australia is more readily influenced by external conditions than that 

 of any other wheats. 



Although the " density " in some countries appears to be so variable 

 that it is of little or no value there for purposes of classification, in other 

 regions it is practically constant under all ordinary conditions of cultiva- 

 tion, and of the greatest service in assisting in the identification of the 

 various forms. 



Empty Glume. The form of the empty glume is one of the most 

 constant characters of wheats, and of the greatest value in distinguishing 

 nearly related forms. In some cases the glumes at the base, middle, and 

 tip of the ear are slightly different in shape and length of the apical or keel 

 tooth, but the glumes from the middle spikelets of ears belonging to plants 

 of the same form are almost exactly alike, and different from those taken 

 from the same parts of the ears of different forms. In some the upper 

 part of the glume is broad, in others it is narrow ; the apical tooth has a 

 characteristic form and size, and the amount of its curvature inward or 

 outward is also a constant feature. These forms unfortunately cannot 

 be adequately described, but must be illustrated. 



Grain. Its colour, flintiness or mealiness, shape and size. 



Other characters which it is important to notice are 



(1) Time at which the ear appears ; 



(2) The tillering capacity ; and 



(3) Resistance to frost, drought, and attacks of insects and fungi. 

 Earliness and Lateness. Wheats are often classified by the practical 



agriculturist into early, mid-season, and late varieties, the terms referring 

 to the time when the grain is fully developed and ripe. The period at 

 which this stage is reached is chiefly dependent upon latitude and climatic 

 conditions and subject to very considerable variation. For example, the 

 same variety of wheat sown at the same date in the same locality may 

 ripen its grain from 1 5 to 20 days or more earlier or later in one season than 

 another, the grain ripening off quickly in a bright dry hot summer, the 

 process being very much delayed by damp dull weather. 



A much more accurate classification is made by referring the terms 

 early, mid-season, and late to the time at which the ear escapes from the 

 upper leaf-sheath. This time for any particular variety grown at any 

 definite locality in England does not vary more than four or five days 

 in any season even when the sowing is carried out during the period 

 extending from September to December. When the sowing is later than 

 this, say in January or early February, the time of appearance of the ear 

 is rarely delayed more than about a week. 



For details of the time usually elapsing between " earing " and 

 ripening of the grain, see p. 142. 



M 



