The Flower and its Parts : Process of Fertilization. 29 



11. Staminate. 



Flowers of the 



Oak enlarged. 



of the blossom is secured whenever the pollen, at maturity, is con- 

 veyed to the stigma of the pistil. 



117. The blossoms of trees are often unsymmetri- 

 cal, and the parts essential to fertilization may be 

 either in the same blossom, as shown on a subsequent 

 page in the linden, or on different parts of the same 

 tree, as shown in the hornbeam and the alder, in the 

 accompanying engravings. In the latter, the germs 

 for the early spring blossoms are formed the fall be- 

 fore. Such pendant blossoms in trees are called 

 aments, or catkins. Their form and structure afford 

 characters, upon which botanical classification in part 

 depends. 



118. Where both the staminate and pistillate blos- 

 soms grow upon the same plant, it is said to be 

 monoecious, but when formed upon different trees or 



plants, as in case of the poplars and willows, it is said to be dioecious. 

 In the latter case, the seeds can not be fertile, unless trees bearing 

 both kinds of blossoms grow 

 in the same neighborhood. 



119. The winds have an 

 important influence in dis- 

 seminating the pollen from 

 one tree to another, and the 

 blossoms of such trees gen- 

 erally open in the windy sea- 

 son of the year, and before 

 the leaves appear. The bees, 

 in pursuit of honey, perform 

 an important office in con- 

 veying pollen from one blos- 

 som to another, and there 

 are many special arrange- 

 ments in nature for securing 

 fertilization. 



120. When the pollen of one species is conveyed to the pistillate 

 flowers of another species, within the same genus, cross-fertilization 

 sometimes occurs. This may occur naturally, or by artificial means, 



12. Two Male Blossoms of the Hornbeam, and 

 the Terminal Pistilate Blossom. 



