48 ELEMENTARY BOTANY. 



4. When pollination is effected by insects, the flowers are 

 said to be entomophilous (Gr. entomon, insect ; philos, loving). 

 In these the amount of pollen produced is not so great, there 

 being but little waste as compared with the loss when trans- 

 ported by the wind. It is not so dry and incoherent as in the 

 anemophilous flowers ; the grains are generally moist or slightly 

 viscid, often provided with projections or entangling threads. 

 In the Orchids and Milkweeds the pollen is in masses, sup- 

 plied with viscid pedicels. All these contrivances tend to in- 

 sure the adherence of the pollen grains or masses to the head, 

 legs, or usually hairy body of the insects which visit the 

 flowers, and thus incidentally effect the transportation of the 

 pollen to the stigmas of other flowers. Such flowers are fur- 

 ther characterized by the possession of a large colored corolla 

 or other showy parts of (or adjacent to) the flower, or of odor, 

 or by the secretion of nectar ; they are often gamopetalous and 

 frequently irregular; or they may furnish all these attractions 

 combined. 



5. Of the special adaptations in hermaphrodite flowers to 

 insure cross-pollination, dichogamy is an important one ; it 

 means that the stamens and pistil of the same flower do not 

 come to maturity at the same time, hence self-pollination is 

 impossible. The flower is proterandrous (Gr. protos, first; 

 andres, stamens) when the anthers ripen and discharge the 

 pollen before the stigma reaches maturity. If the stigma is 

 in a receptive condition before the pollen escapes, the flower is 

 proterogynous (Gr. protos, first ; gyna, pistil). Among the 

 anemophilous flowers the common Plantain furnishes an ex- 

 ample of proterogyny. The long, slender, hairy stigmas may 

 be seen protruding from the unopened perianth while the an- 

 thers are yet enclosed. Only pollen from other flowers, there- 

 fore, can effect the pollination. Later the stigmas wither, and 

 the corolla expands ; the four anthers now appear supported 

 on long, delicate filaments and their pollen is carried to stigmas 

 of other Plantain flowers which may have a synchronous 

 maturity. 



6. A proterogynous example among entomophilous flowers 



