GENERAL CONSIDEBATIONS. 109 



Hence when the student has acquired a knowledge of the 

 anatomy and functions of leaves, he is prepared to enter on 

 the consideration of the floral organs. 



It has been shown that every plant which consists of more 

 than one cell, or of a series of cells united together, may be 

 divided into two distinct parts, to which separate functions are 

 assigned, a vegetative part and a reproductive part. In the more 

 highly organized plants, the vegetative part of the plant con- 

 sists of the root, the stem, and the leaves, each having distinct 

 functions assigned in the vegetable economy. Now every 

 plant continues to grow so long as its vegetative cells continue 

 to develop ; but when the plant acquires all its developments, or 

 arrives at an adult state, the reproductive cells show them- 

 selves, and growth stops in that direction : the whole force of 

 vegetation being expended in the production of the spore or 

 seed, the embryo or germ of the future plant. 



In the more highly organized plants, the cells which are 

 connected with reproduction make their appearance in the 

 form of beautiful whorls of metamorphosed and colored leaves, 

 constituting that part of the plant which is popularly called 

 the flower ; and we are about to trace those curious processes 

 which are carried on by them, or their physiological action in 

 the production of the embryo or seed, which contains within 

 itself the rudiments of future generations. 



That flowering is an exhaustive process and' therefore 

 necessarily causes the cessation of the growth or extension of 

 the parts of plants, is evident from the following facts. Plants 

 will continue to grow if the flower buds are removed as soon 

 as they are formed. This is often done by gardeners, who nip 

 off' the young flower buds in order to encourage the growth of 

 the plant, which is thus enabled to accumulate a greater store 



10* 



