CATKINS 



after reaching the stigma. A kind of germina- 

 tion takes place, and the httle grain develops a 

 delicate tube which penetrates the tissues of the 

 stigma. This tube travels right away to the 

 embryo seed within the heart of the catkin, the 

 fertilising element of the grain being thus con- 

 veyed to the future seed, which afterwards rapidly 

 develops. A glance at Fig. 36 (Plate 23) will 

 show that the extremely minute pollen grain must 

 extend a tube many hundreds of times longer than 

 its diameter to reach the embryo seed within the 

 catkin. In Fig. 38 (Plate 24) is shown a section 

 of the stigma of a flower of the evening primrose, 

 to show how pollen tubes penetrate the tissues of 

 the stigma. This example is used for illustration 

 because the pollen grains and tissues of the even- 

 ing primrose are larger and more suitable for 

 photographic purposes. However, the movements 

 of the pollen tubes through the stigmas of the 

 hazel catkins are practically the same. 



In the previous chapters I have called attention 

 to the devices which insect-pollinated flowers 

 employ to effect cross-pollination, by means of 

 which stronger and better seeds are produced. 

 The hazel attains that end by producing its male 

 and female flowers in separate catkins ; and as the 

 male catkins are pendulous, while the female are 

 held upright, the latter are much more likely to 

 receive pollen blown from other quarters than 

 from their immediate neighbours. 



Having thus dealt in detail with the hazel, my 

 reader will now be able to investigate, on his own 



55 



