THE "WILD "WHEAT OF PALESTINE 303 



place without the flowers opening (pseudo-cleistogamous 

 fertilization).^' 



Rimpau has also observed the effects of temperature on 

 the opening of wheat flowers. He states that at 12°-13°0. 

 (54°— 56°r.) the glumes do open a little but that com- 

 plete opening does not take place under 16°C. (61°F.). 

 He found that the opening of the glumes is not limited 

 entirely to the morning hours but may take place at any 

 hour of the day or even in the evening. The length of 

 time during which the flowers are open depends on the 

 temperature and the dryness of the air: at 23°C. (73°r.) 

 the flowers closed again in 15-20 minutes, but at lower 

 temperatures closing took a much longer time. Rimpau 

 observed that the anthers dehisce before they have reached 

 the upper margins of the glumes by elongation, so that 

 automatic self-pollination is regularly effected in every 

 flower.^* 



Eimpau removed the anthers from 85 wheat flowers and 

 yet 50 of them set fruit. He therefore concluded that if 

 self-pollination were not to take place, pollination by 

 crossing would still ensure the production of seed. He 

 found that crossing, as judged by the average number of 

 haulms formed, gave rise to a more vigorous off-spring 

 than self-pollination, the result being seen even in the 

 fourth generation.^® 



The flowers of wheat only open once and for a very short 

 time. The actual opening which results in the divergence 

 of the glumes and the exposure of the sexual organs, is 

 effected by two small scales known as lodicules which lie at 

 the base of the flower between the ovary and the outer 

 glume. Aa a flower opens, the lodicules become fleshy and 



23 Ihid. 



24 Ibid. 



25 Ibid. 



