45 



which the stamens are lacking is known as a pistillate flower. Some- 

 times the staminate and pistillate flowers are not only found on dif- 

 ferent parts of the same tree but on entirely different trees. 



The chief role of flowers is pollination. Pollination is the transfer 

 of pollen from the anther of the stamen to the stigma of the pistil. 

 When pollen is transferred from the anthers to the stigma of the 

 same flower it is known as close-pollination, and when pollen is trans- 

 ferred from the anthers of a flower of one plant to the pistil of a 

 flower of another it is known as cross-pollination. Wind and in- 

 sects are the chief agents which carry the pollen in the case of cross- 

 pollination. The flowers of the Tulip Tree, Papaw, and Cherries, are 

 examples in which close-pollination can take place, while the flowers 

 of the Willows and Poplars are good examples in which cross-polli- 

 nation takes place. When the staminate and pistillate flowers are 

 on the same plants e. g. Oaks, American Hop Hornbeam, Beech, 

 Chestnut, Hickories, and Walnuts, the plants are known as 

 monoecious and when they are on different plants as in the Willows, 

 Poplars, and occasionally some Maples, they are known as dioecious. 



Flowers vary not only in the size, form, shape of their parts, and 

 color, but also in their arrangement. In a few cases the flowers 

 of trees like the Tulip Tree and Papaw are borne singly and known as 

 solitary flowers. The flowers may also be arranged in clusters like 

 that of the Lily of the Valley or the Wild Black Cherry (Plate VIII, 

 13). Such an inflorescence is known as a raceme. A raceme may be 

 compact as in the Wild Black Cherry; or loose as in the Common 

 Locust (Plate VIII, 3) and the Striped Maple (Plate VIII, 4-5). 

 When the flower cluster is dense and the flowers sessile, or nearly 

 so, it is known as a spike. Spikes may be 2-5-flowered as in the 

 pistillate flowers of the Hickory (Plate VII, 8), or densely flowered 

 as in the staminate flowers of the Mulberry (Plate VII, 18). A 

 very short and dense spike is known as a head (Plate VIII, 14). A 

 spike is sometimes short, flexible, and rather scaly as in the Willows, 

 Poplars, and rather long as in the staminate flowers of the Oaks, 

 Hickories, Birches, and Alders (Plate VII, 7, 9 and 15). Such a 

 spike is known as an ament or catkin. Other types of inflorescence 

 are the umbels (Plate LXXXVII), panicles (Plate VIII, 10-11), and 

 corymbs. 



The time at which the flowers appear and their duration varies 

 with the species. The Alders, Hazlenut, and some Maples produce 

 their flowers early in spring before the leaves are out. Others pro- 

 I duce them with the leaves, while still others produce them after the 

 leaves. The Witch-hazel produces its flowers late in fall. It is the 

 last of our trees to blossom. 



