INTRODUCTION 9 



the pollen necessary to fertilize the ovules. Usually 

 petals and sepals (non-essential organs) are associated 

 with the essential organs, either for protection or to 

 attract insects, humming birds and other creatures upon 

 which fertilization of many plants depends. Some 

 flowers, such as lizards-tail, are naked ; that is, they have 

 neither petals nor sepals, at least during the fertilizing 

 period. Others, such as snowball and hydrangea and the 

 ray flowers of many composites, often have neither pistils 

 nor stamens. They are, therefore, called sterile. 



19. The pistil consists of two essential parts, the stigma 

 and the ovary. It may or may not have a style or stalk 

 joining these two parts; or rather, when the style is very 

 short it is said to be sessile. 



20. Ovules are small growths on the interior walls of 

 the ovaries. They usually consist of two layers, which 

 inclose the embyro sac. This sac consists of several 

 cells, one of which is the egg cell. 



21. Fertilization of flowers is the rendering viable of 

 ovules by the pollen. It is almost always between plants 

 of the same species, and usually between flowers of dif- 

 ferent plant individuals. When plants of different species 

 or genera unite by means of the pollen of one fertilizing 

 the ovules of another, the resulting plants are called 

 hybrids. Comparatively few tree fruits will hybridize, 

 but several of the bush fruits and many ornamental 

 plants have done so. Almost always hybrids of trees 

 and shrubs must be propagated asexually. 



Examples of hybridization are Kieffer, Le Conte and Garber pears, 

 Rogers' grapes, wild goose plum, Wilson blackberry, Shaffer rasp- 

 berry and many varieties of roses, cannas, begonias, gladioli, 

 fuchsias, etc. 



22. The fertilization process in flowers is essentially as 

 follows : Ripe pollen is discharged from the anthers in 

 the same or some other flower, generally of the same 

 species. It reaches the "ripe" or receptive stigma of the 

 pistil either through the agency of wind, insects or some 



