43^ 



KELATION TO ENVIRONMENT, 



i.e. the pollination of the pistil of one flower by pollen from another, is 

 sure to take place, if it is pollinated at all. Even in moncecious plants cross 

 pollination often takes place between flowers of different individuals, so that 



Fig. 45+- 

 Viola cucullata ; blue flowers above, clcistogamous flowers smaller and cur^'ed below 

 Section nf pistil at_right. 



more wiilely different stocks are united in the fertilized egg, and the strain 

 is kept mure vigorous than if very close or identical strains were united. 



848. i hit there are many flowers in which both stamens and pistils are pres- 

 ent, and yet in which cross pollination is accomplished through the agency ol 

 insects. 



859, Pollination of the bluet. — In the pretty bluet the stamens and 

 styles of the flowers are of difterent length as shown in flgures 4=;s. 4=;6. 

 The stamens of the long-styled Mower are at alumt the same level as the 

 stigma of the bhort-styled flower, while the stamens \j{ the latter aieon 



