266 - GENERAL SCIENCE 



ment of the ovules into seeds. In due time the enlarged 

 ovary becomes the ripened fruit, and the ovules ripened 

 seeds. The ovary wall itself may become juicy as in the 

 currant, grape, and tomato, or it may become a shell as in 

 the walnut. 



In many plants all these acts of fertilization occur within a 

 single flower; in others the pistillate and staminate flowers 

 occur in different parts of the same plant, and sometimes 

 they are borne on entirely different plants. 



The petals taken together form the corolla whose bright 

 colors in many flowers undoubtedly attract insects as agents 

 in pollination. The small green sepals forming the calyx 

 serve in the bud of the unopened flower to protect the en- 

 closed parts from cold and wet and from insect enemies. 

 In the process of the development of the flower the calyx 

 may become greatly modified, even into such structures as 

 the pulp of the apple and pear. 



It is to be kept in mind in all studies of flowers, and of 

 plants in general, that variation rather than uniformity is 

 the rule. Any extended study of flowers and plants from 

 the specimens themselves soon reveals the fact that the 

 adaptability of plants to varying conditions affecting their 

 lives is one of the wonderful features of plant development. 



Many plants that bear seeds are independent of these seeds 

 for their propagation. Each generation may provide for 

 new plants by the growth of creeping stems or " runners" 

 as in the strawberry, or by bulbs as in the onion, lily and 

 tulip, or by underground stems as in the hop plant and the 

 common potato. Seedless oranges are secured by grafting 

 into small orange trees of the common sort twigs that 

 have been cut from an orange tree whose fruit persistently 

 fails to develop seeds. Bananas are raised from sprouts aris- 

 ing from the old roots. Florists and nursery men use short 

 lengths of the stems of some plants, such as the geranium, 



