WILD FLOWERS OF NEW YORK 27 



this is not wholly true. The subject of pollination of flowers by insects 

 received a great light through the investigations of Charles Darwin and the 

 publication in 1862 of his well-known book on the fertilization of orchids 

 by the aid of insects. 



As we understand the matter today, it appears that flowers are habitu- 

 ally intercrossed (flowers of the same species), and that there are manifold 

 structural adaptations which secure or favor this interchange of pollen. 

 Separation of sexes (stamens and pistils) is a direct adaptation to cross- 

 pollination, rendering it necessary between individuals with dioecious 

 flowers, and favoring it in most plants with monoecious and polygamous 

 flowers. Strictly, close fertilization can take place in hermaphroditic 

 flowers only. 



Flowers depend upon certain external agencies for the transference 

 of pollen from one flower to the flower on another plant. These agencies 

 are wind (anemophilous flowers) and insects (entomophilous flowers). 

 Other agencies are of minor importance, although water must be considered 

 in connection with some aquatic plants. 



Wind-pollinated flowers are mostly dull in color, destitute of odor and 

 nectar, since these qualities attract insects. Wind-pollinated flowers 

 usually have the sexes separated, the flowers borne in great abundance 

 and have very light pollen. Most of our common trees (the Pines, Oaks, 

 Hickories etc.) depend upon wind for the transference of pollen, as do also 

 the grasses, sedges, Plantain and others. 



Insect-pollinated flowers are correlated with showy coloration (includ- 

 ing white, which is most showy at dusk), odor or secretion of nectar. 

 Structural adaptations of the flower in reference to insect visitation are 

 wonderfully various, and most of these are found upon investigation to 

 favor, or often to necessitate, cross-pollination. The range of these varia- 

 tions is too extensive to be treated here. Literature upon this subject is 

 easily available and most textbooks of botany contain chapters upon the 

 subject. 



After pollination the pollen grain germinates upon the surface of the 



