6 4 



PART I. ORGANOGRAPHY. 



The parts are represented as separated in their order from the 

 receptacle : 



(a) Represents a whorl of three pistils, the gynaecium. 



(b) A whorl of three stamens, the androecium. 



(c) A whorl of three petals, the corolla. 



(d) A whorl of three sepals, the calyx. 



(e) The receptacle, the shortened axis on which all these 

 parts are inserted ; and 



(f) A bract below the flower. 



Fig. 203. 



Fig. 202. — Diagram of a typical flower; 

 a, the pistils; 6, the stamens; c, the corolla; 

 d, the calyx; e, the receptacle, and./, bract. 



Fig. 203. — Ground plan of the same 

 flower, showing relation of parts. 



Fig. 203 represents the 

 ground plan of such a flower. 

 The first, or outside whorl, rep- 

 resents the calyx, the second 

 the corolla, the third 

 the androecium, and the 

 fourth, or central whorl, 

 the gynscium. It will 

 be observed that the 

 successive whorls alter- 

 nate with each other, or 

 are arranged on the same plan as whorled leaves. 



It will also be seen that in this ground plan a certain num- 

 ber, the number three, prevails throughout. This is called the 

 numerical plan of the flower, a very important thing to observe 

 in the study of flowers, since in some large groups of plants the 



Fig. 202. 



