THE PISTIL. 



91 



EXERCISE XXXI. 

 Placentation. 



After studying the structure of ovaries as ex- 

 plained in Ex. XXX., the following definitions will 

 be easily understood : 



PLACENTATION. The arrangement of placentae is 

 called placentation. 



To determine the mode of placentation of a plant, 

 slice its ovary across, and compare its appearance with 

 the following figures. The formation and arrange- 

 ment of placentae are so various, that we have given 

 an unusual number of drawings to illustrate the defi- 

 nitions. 



AXILLARY PLACENTATION. When the ovules are 

 found along the central line, or axis of the pistil, the 

 placentation is called axillary r , or axile (Figs. 169, 170, 

 ITl, 172, and 173). 



Fio. 169. 



FIG. 170. 



FIG. 171. 



FIG. 172. 



FIG. 173. 



