Just as we have male and female in the animal world, so we 

 have male and female in the plant world. A few of our trees, 

 as the Locust, Basswood and Cherries have perfect flowers, bear- 

 ing both stamens and pistil. The great majority, however, have 

 unisexual flowers, bearing stamens or pistils, but not both. When 

 both male and female flowers are found on the same tree, the 

 flowers are said to be monoecious, and when male flowers occur 

 on one tree and the female on a different tree, the flowers are 

 said to be dioecious. The Cottonwood is dioecious, and the 

 little seeds are surrounded by a tuft of long, white hairs which 

 enables the wind to carry them to considerable distances from the 

 parent tree, to the disgust of people living within range. Many 

 cities forbid the planting of Cottonwood on account of the 



V. TYPES OF INFLORESCENCES 



Spike. Raceme. Panicle. Corymb. 



Umbel. 



Cyme. 



"cotton." Since in some cases it is desirable to plant this rapid- 

 growing tree, as in cities burning large amounts of soft coal, it 

 is a distinct advantage to know that male trees are lacking in the 

 objectionable "cotton" and may be planted safely. 



Before trees can produce fruit their flowers must be fertilized, 

 i. e., pollen from the anther of a stamen must come in contact 

 with the stigma of a pistil. Some flowers are self-fertilized, 

 others are cross-fertilized. For a long time it was not known 

 how fertilization was accomplished, but now we know that many 

 insects, like the nectar-loving bees and butterflies, and in other 

 cases the wind transport the pollen from one flower to another, 

 often miles being traversed before the right kind of flower or a 

 flower in the right stage of development is found. And many 

 are the modifications of flowers to insure this transference of 

 pollen. 



FRUIT. So numerous and so varied are the forms of tree 

 fruits that it would only be confusing to enumerate their various 

 characters. Some fruits, as the achenes of the Poplars and Wil- 

 xiv 



