PLANT LIFE. 47 



curs. However, it is known that often pollen of a 

 closely related kind of plant is able to cause fertiliza- 

 tion and produce seeds capable of germination. This 

 is called hybridization. The plants growing from 

 these seeds usually show more or less of a blending 

 of the character of the two parents, or some characters 

 of the one and some of the other. Many such hybrids 

 occur in nature, but more are known as the result of 

 human effort. 



Fruit and Seed Distribution. After pollination, 

 when the seeds begin to grow there begins the forma- 

 tion of what is termed, botanically, a fruit. Used in 

 this sense a fruit is any structure, whether edible or 

 inedible, fleshly or dry, that is produced to accompany 

 or enclose the seeds. Usually the corolla falls off 

 and often the calyx as well. In the simplest fruits the 

 ovary simply enlarges and forms a sort of pod which 

 becomes dry as the seeds ripen and splits open to let 

 them escape. Examples are the bolls of cotton, pods 

 of beans, peas, mustard, etc. In other cases the outer 

 part of the ovary becomes fleshy and edible with the 

 result that it is sought after by animals for food, the 

 seeds being carried thus to various distances. Cher- 

 ries, plums, etc., are good examples of this class. The 

 calyx, too, may become fleshy or the flower stalk or 

 the flower axis. The latter is the case in the straw- 

 berry. The ovary, or the parts outside of it, may de- 

 velop hooks to catch in animals' hair to aid in distri- 

 bution, or the calyx may have a downy structure for 

 wind conveyance as in the thistle or dandelion. The 

 seeds often have various devices to aid in distribution 

 by wind, water or animals. A few fruits explode 

 throwing the seeds out to a great distance. 



Kinds of Seed Plants. There are two great sub- 

 divisions of seed plants; the flowering plants with real 

 flowers, with the seed produced inside of the ovary 

 and the Gymnosperms where no true flowers occur, 

 with the seed produced on open scales. Usually these 

 scales are bunched together into a dry or fleshy cone. 



