THE FLOWER. 25 



halation of oxygen. In their green cells and in other green parts of 

 plants are carried on the functions of digestion and assimilation and the 

 manufacture of the multitude of principles which give to plants their 

 peculiar properties. Wherever these principles may be stored up, whether 

 in the roots, the stem, the bark, the fruit, or in the leaves themselves, 

 they are the product of the green cells, which attain their greatest develop- 

 ment in the expanded leaves. 



THE FLOWER. 



Having studied the organs by which plants develop and exist as individ- 

 uals, we have next to consider those engaged in the process of reproduction. 



At an established period in every flowering plant's life, the terminal or 

 axillary buds cease to produce leaves, their leaflets undergoing a transfor- 

 mation by which they become reproductive organs. A bud in this trans- 

 formed condition is termed a flower- bud, and when fully expanded be- 

 comes a flower. 



We have already seen that leaf-buds are not scattered hap-hazard along 

 the stem, but are arranged in a fixed, determinate manner ; now, as flower- 

 buds are but transformed leaf-buds, we are prepared to find them also oc- 

 cupying fixed positions. This arrangement of flowers is termed Inflo- 

 rescence, and demands a brief examination before proceeding to the 

 consideration of the structure of the flower. 



In some plants only the buds terminating the main stem and branches 

 are transformed into flowers ; in others, only the axillary ; in others still, 

 but much more rarely, the flowers are both axillary and terminal. 



When the flowers are all terminal the inflorescence is termed deter- 

 minate ; when they are all axillary it is termed indeterminate, because 

 so long as the terminal bud continues to produce leaves with buds in their 

 axils, flowers follow as a matter of course, and their number is indefinite. 



The organs of inflorescence are bracts, peduncle, pedicel, and 

 receptacle. 



B racts are altered leaves from the axils of which the floral axes spring ; 

 they may be foliaceous, membranous, scarious, or petaloid (colored). Sec- 

 ondary bracts that is, those at the base of secondary divisions of a floral 

 axis are termed bract lets. 



A peduncle is a branch directly terminated by a flower ; and its ex- 

 tremity, usually more or less enlarged, upon which the floral organs proper 

 are seated, is the receptacle. 



A pedicel is a secondary peduncle, or in other words, the stalk upon 

 which an individual flower of a branching inflorescence is situated. 



Indeterminate inflorescence presents five well-marked forms, 

 termed the raceme, corymb, umbel, spike, and head, each of which 

 is subject to various modifications. 



