62 THE DEVELOPMENT OF KAW COTTON 



setting free the pollen-grains. By the evening the corolla 

 has faded, turning in the process to pink and red colours 

 if the fading is taking place in damp air, or simply drying 

 up if the air is dry, with the colours almost unchanged. 



Meanwhile pollen has reached the style, either by 

 accident or brought by bees, which have visited the flower 

 for the honey which it secretes from the nectaries between 

 the bases of its petals. In either case the pollen may be 

 derived from the same flower or from a foreign flower. 

 In the former case the flower is self-f ertilized ; in the 

 latter it is "crossed," and this latter event happens in 

 5 to 10 per cent, of the seeds ripened in an Egyptian 

 field. Lastly, if in the latter case the pollen is derived 

 from an identical brother-plant, such as another member 

 of the same pure strain, the effect is the same as self- 

 fertilization ; but if as is likely to be the case in 

 commercial varieties the pollen-parent is not exactly 

 identical, the effect is to produce a hybrid embryo, and 

 consequently a hybrid plant in the following season. The 

 exclusion of such foreign pollen (PI. XIII.) is the great 

 difficulty confronting those who attempt to introduce new 

 varieties of cotton or to improve old ones. 



The action of the pollen is very like that of a parasitic 

 fungus. The pollen-grain germinates when placed on the 

 style or in a 2 per cent, solution of sugar, and sends out 

 a tube, which grows between the cells of the style tissue, 

 through the inner walls of the ovary, and enters the 

 cavity of the ovary. There its end creeps over the surface 

 of the ovules until it enters the small hole left by the 

 seed-coats. Passing down this canal through the two 



