The Flower. 95 



edge of the cultivator, if his trees of bearing age cannot 

 form flower-buds without such choking. 



Fruit trees grafted on slightly uncongenial stocks 

 sometimes flower and fruit more freely for a time than 

 when growing on their own roots, because the imperfect 

 union of cion and stock (383) forms an obstruction to 

 the rootward food-current. 



SECTION X. THE FLOWER. 



138. The Flower is the developed and expanded 

 flower-bud (131). Its office is to provide for the for- 

 mation of new plants of its kind (reproduction, (16)). 

 Some plants, as the quack grass,* Canada thistlef and 

 horseradish^ multiply freely in nature without the aid 

 of flowers, and nearly all plants may be multiplied in 

 culture by other means, but in most of the higher 

 plants, the flower is the natural organ of reproduction, 

 and the only organ devoted solely to this end. 



139. Flowers Tend to Exhaust the Plant, since they 

 are formed from the food prepared by the leaves. But 

 since flower-buds are not usually formed until the needs 

 of growth are provided for (134 A), the normal pro- 

 duction of flowers does not injure the plant. In cer- 

 tain cases, however, as in plants weakened by recent 

 transplanting or in cuttings (358), flower-buds should 

 be removed as soon as discovered, to prevent their ex- 

 haustive influence. 



140. The Parts of the Flower. The complete flower 

 is composed of four different parts or organs. A knowl- 

 edge of these parts is of great importance to the botan- 



* Agropyrum repens. f Cnicus arvensis. | Nasturtium Armoracia. 



