124 THE WHEAT PLANT 



completed after the latter is pushed out of the flower, a large proportion 

 of the pollen being shed into the air. In many flowers all the anthers 

 are carried into the open air at the time of anthesis, but quite frequently 

 one or more fail to escape from the glumes, being entrapped behind the 

 folded margin of the palea or caught between the tips of the closing glumes. 

 Retention of the anthers, which is most frequent in dense-eared wheats, 

 occurs chiefly in the lower spikelets of ears and the smaller flowers of each 

 spikelet, some of which do not open at all. Of flowers which open, the 

 glumes generally remain widely separated from 5 to 15 minutes and then 

 slowly close again, the lodicules meanwhile becoming flaccid ; the time 

 taken in opening and closing completely varies from 8 to 30 minutes or 

 more, the average being about 20 minutes. 



Anthesis occurs in the early part of June at Reading, the individual 

 flowers opening at various times of the day, from dawn till an hour or two 

 after sunset. 



Observations upon representatives of the chief kinds of wheat revealed 

 no characteristic specific differences ; flowering was observed to occur 

 during most hours of daylight, but it was especially frequent between the 

 hours of 5-7 A.M., 9-10 A.M., 2-3 P.M., and 8-9 P.M. Meteorological con- 

 ditions appear to influence the time at which it takes place. Gitkova at 

 Saratoff, Russia, found the flowering of a variety of T. mdgar e and T. 

 durum was most intense between 5 and 7 A.M., with a second maximum 

 between 5 and 6 P.M. Leigh ty and Hutcheson also noted two periods 

 of extensive blooming during daylight, namely, from 7 to 9 A.M., and in 

 the middle of the afternoon, with a secondary morning period about 



II A.M. 



The basal flower is the first to open in each spikelet, the others following 

 in regular succession upwards. 



The position of the first spikelet to flower varies a little ; it is generally 

 in the middle third of the ear, and usually near the upper part of this 

 section, except in the case of T. aegilopoides, T. monococcum, and T. dicoc- 

 coides, in which the spikelets to open first are nearer the tip, at a point 

 about the middle of the upper half. 



In ears possessing 16-18 spikelets the 8th to the i2th usually open first ; 

 in those with 28-30, the i6th to 2Oth. Anthesis proceeds upwards and 

 downwards from these points in more or less regular succession, the apical 

 and basal spikelets being the last to flower. Sometimes 4 or 5 spikelets 

 on one side open before the rest ; in other cases adjacent spikelets on 

 opposite sides of the rachis flower almost simultaneously. 



The successive flowers of a spikelet usually open on successive days, 

 but occasionally two of the same spikelet open on the same day, one in 

 the morning, the other later, after an interval of 5 or 6 hours. 



At Reading the whole ear often completes its flowering in 3 to 5 



