THE STEMS 



when the two are sown together, no matter where or in what season the 

 experiment is carried out, although, as mentioned hereafter (p. 91), the 

 time required by a wheat to reach the " earing " stage may be 300-320 

 days or only 60-70 days according to the time at which its grain is sown. 



Each form of wheat sown on a particular date in England shows 

 remarkable regularity in the production of its ears : in normal seasons 

 the latter frequently appear on the same day in each year, and only in 

 years of drought or unusual rainfall is the time of their escape from the 

 leaf-sheaths accelerated or retarded more than a week or ten days. The con- 

 stancy of this character is of use in distinguishing closely allied forms, where 

 these can be grown together and observations made during several seasons. 



For purposes of description and classification wheats may be grouped 

 into " early," " mid-season," and " late " forms, the former usually 

 exposing their ears at Reading before the end of May, the latter during the 

 second or third week in June. 



In the following table is given the usual date of " earing " of over 

 1 500 wheats when sown in September or October at the University College 

 Farm, Reading : 



Although the date of " earing " of a wheat when sown at a particular 

 time is almost constant, the exit of the ear from the leaf-sheath may be 

 arranged to occur early or late over a fairly wide period of the summer 

 by altering the time of sowing. If, however, it does not take place before 

 the first week or ten days of July there is rarely sufficient time for the grain 

 to ripen at Reading (see pp. 90-92). 



