THE FLOWER 123 



At the time of anthesis the thin-walled parenchyma of the lodicules 

 becomes very turgid, the outer face of the tissue assuming a convex form. 

 The two lodicules in this swollen state act as clastic cushions which push 

 apart the flowering glume and palea, the separation taking place rapidly, 

 often attaining a maximum in five minutes or less. Very slight mechanical 

 stimulus either affects the turgidity of the lodicules or releases the edges 

 of the glumes from each other, for the opening of the glumes often takes 

 place rapidly, on gently running the ear through the hand, by touching 

 the awns, or by the impact of the ears against each other as they are 

 swayed to and fro in a breeze. 



The angle of separation of the glumes varies considerably. In T. 

 aegilopoides, T. dicoccoides, and T. dicoccum, and in some varieties of T. 

 vulgare, it may reach 40 or more, especially in bright warm weather ; in 

 the majority of cases, however, it does not exceed 2O-3O, and in T. Spelta, 



In.. 102. Anthctis of lowest flower of a tpikelet. a. 8.48 A.M. ; b, 8.50 A.M. ; 

 c, 8.56 A.M. ; d, 9.7 A.M.. June 19. 1915 ( * a). 



T. compactum, and certain forms of T. polonieum and 7*. rulgare it is often 

 less than this. 



As soon as the glumes begin to separate, rapid changes occur in the 

 floral organs. The styles, which at first lie close together and parallel 

 to the long axes of the ovary, quickly curve away from each other, and the 

 feather)' stigmas spread out ; in most wheats these remain within the 

 glumes, but in some varieties their tips may be seen projecting on opposite 

 sides of the flowering glume. At the same time the filaments of the 

 stamens lengthen rapidly, expanding from a length of 2 or 3 mm. to 7-10 

 mm. in two to four minutes, and the anthers are thrust out of the opening 

 between the glumes, usually on the outer face of the spikelet (Fig. 102). 



The pollen-sacs commence to dehisce when the filaments begin to 

 lengthen and a variable amount of pollen is left in each flower ; self-pollina- 

 tion is the rule. 



Dehiscence progresses from the tip to the base of the anther, and is 



