300 ESSAYS ON WHEAT 



tered by the wind, and the spreading of the glumes permits 

 wind-blown pollen to fall upon the stigmas. The two 

 glumes of a flower, when opening occurs, separate at an 

 angle of from 30° to 40° so as to form a broad tube or 

 funnel with the expanded stigmas at the bottom. Al- 

 though well protected on all sides, the stigmas can be seen 

 in the open flower by looking in from above.-'® 



Cook, when studying pollination in the wild wheat, 

 found indications of sexual dimorphism,-''^ i. e., that there 

 are two forms of flowers regarded sexually. In some 

 plants which he examined, the flowers were proterogynous, 

 the stigmas being exposed before the adjacent anthers 

 had matured, whilst in other plants the flowers appeared 

 to be protercmdrous, the anthers being exserted at a time 

 when the stigmas were still only partly developed. Seed 

 was also found to be produced in some heads that had not 

 emerged from their sheaths, from which we may con- 

 clude that some forms of Triticum hermonis are capable of 

 self-fertilizing their own flowers. Cook's observations go 

 to show that in the wild wheat of Palestine the usual 

 mode of pollination is cross-pollination. 



The Grass Family or Graminese, as a group, possesses 

 flowers with floral mechanisms adapted to secure cross- 

 pollination; and, for grasses in general, we must look 

 upon this mode of pollination as primitive and ancestral. 

 The wild wheat of Palestine, which is a wild grass, there- 

 fore resembles most other grass species in having cross- 

 pollinated flowers. In our cultivated wheats, on the other 

 hand, self-pollination is the rule, although cross-pollina- 

 tion may and does take place occasionally.^* We may 



16 lUd., p. 15. 

 " Hid. 



18 Tide Chapter IV, Section V, on Red Bobs the Product of a Natu- 

 ral Cross. 



