' 
90 Principles of Plant Culture. 
stock (379) forms an obstruction to the rootward food- 
current. 
Section XI. THE FLoweEn 
139. The Flower is the developed and expanded flower- 
bud (132). Its office is to provide for the formation of new 
plants of its kind (reproduction (16)). Some plants, as the 
‘quack grass,* Canada thistlet 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. 
140. Flowers Tend to Exhaust the Plant, since 
they are formed from the food assimilated by the leaves. 
But since tlower-buds are not usually formed until the needs 
of growth are provided for (135), the normal production of 
flowers is no detriment to the plant. In certain cases, how- 
ever, as in plants weakened by recent transplanting, or in 
cuttings (358), flower-buds should be removed as soon as 
discovered, to prevent their exhaustive influence. 
141. The Parts of the Flower. The complete flower 
is composed of four different parts or organs. A knowledge 
of these parts is of greut importance to the botanist in 
determining species, and also to the plant breeder who 
would practice cross-pollination (153, 441), hence we need 
to consider them in detail. The cherry blossom, of which a 
vertical section appears in Fig. 43, will serve as our first 
example. 
142. The Calyx (ca’-lyx). Beginning at the bottom, 
the part marked C in the figure, and which is green in the 
* Agropyrum repens. + Cnicus arvensis. t Nasturtium Armoracia. 
