FLOWERS, FRUITS, AND SEEDS 



369 



[Chap. XXXII 



Seeds may be scattered by wind, by water, by birds and other animals, 

 and by means of temporary lodgment on moving vehicles, such as auto- 

 mobiles, airplanes, trains, and ships. Perhaps the most important natural 

 agent in the dissemination of seeds is the wind. Many seeds are light in 

 weight, have relatively large surface areas, and may be carried many 

 miles by air currents. Larger and heavier seeds may be washed great 

 distances downstream, particularly during time of flood. Animals scatter 

 seeds in several ways: (1) the seeds may be eaten and survive the 



Fig. 164. Fruits frequently transported by animals: A, beggar-ticks (Bidens); 

 B, Spanish needles (Bidens); C, sweet cicely (Washingtonia) ; D, tick trefoil 

 (Desmodiiim) ; E, cocklebur (Xanthium) ; and F, sand bur {Solanum) . Courtesy 

 of World Book Co. 



digestive juices of the animal; (2) the walls of the fruit enclosing the 

 seeds may be spinous, prickly, or otherwise roughened and become en- 

 tangled in the fur and hair of animals; (3) the fruit coats may be sticky 

 and adhere to the feet of birds or other animals (Fig. 164). Man is one 

 of the main agents in the dispersing of seeds, especially when it comes to 

 carrying them across the continent or from one continent to another. 

 Dissemination of seed does not necessarily result in the wider distribu- 

 tion of the plant. Germination of the seed does not occur except when 

 the environment is favorable; and even then the seedling may fail to 

 develop or may be destroyed. 



Economic value of flowers, fruits, and seeds. These three plant organs 

 are the primary economic products of floriculture, horticulture, and 

 agronomy. Corn in the United States alone is a billion-dollar crop. This 

 is its value to those who cultivate and harvest it. It may then be con- 

 verted to pork in the body of a pig, or to eggs in the body of a chicken; 

 or man, by means of industrial processes, may place it on the market as 

 meal, corn flakes, hominy grits, starch, glucose, syrup, alcohol, acetic 

 acid, dextrin, mucilage, sizing paste, corn oil, artgum, rubber, or any 

 one of a hundred other products. The economic value of a plant organ 



