IV. FLOWERS AND THEIR WORK 



Problem VI. The structure and work of the parts of a 

 flower. (Laboratory Manual, Prob. VI.} 



Structure of a Simple Flower. Flowers of different kinds of 

 plants vary greatly in size, shape, and color. In our study of the 

 flower our problem will be primarily to find out the use of the 

 flower to the plant which produces it. To solve this problem we 

 must first learn something of the structure and uses of the parts 



of a very simple flower. Examples of 

 such flowers are the evening primrose 

 and the sedum (live-forever), both of 

 which are plentiful in the fall. 



^ll^Ss^^yj The Floral Envelope. In such a 



flower the expanded portion of the 

 flower stalk, which holds the parts of 

 the flower, is called the receptacle. 

 The five green leaflike parts covering 

 the unopened flower are called the sepals. 

 Sometimes the sepals are all joined or 

 united in one piece. Taken together, 

 they are called the calyx. The sepals 

 come out. in a circle or whorl on the 

 flower stalk. 



The more brightly colored structures 

 are the petals. They form the corolla. 

 The corolla is of importance, as we shall see later, in making 

 the flower conspicuous. 



The Essential Organs. A flower, however, could live without 

 sepals or petals and still do the work for which it exists. The 

 essential organs of the flower are within the so-called floral en- 

 velope. They consist of the stamens and carpels (or pistil), the 



34 



A flower of the sedum, from the 

 side, considerably enlarged ; 

 A, anther of stamen ; C, car- 

 pel ; F, filament; P, petal; 

 S, sepal. 



