FLOWERS 



33 



wise; notice that the style appears to be composed of rather spongy 

 material m the interior; the ovary is hollow and is seen to contain a num- 

 ber of rounded structures 

 which appear to grow out 

 from the wall of the ovary. 

 These are the ovules. The 

 compartments in which they 

 grow are called the locules. 

 How many locules do you 

 find in a cross section of 

 the lily ? ^ That part of the 

 ovary wall from which the 

 ovules are outgrowths is 

 called the placenta (plu. 

 placentcB). How many pla- 

 centae do you find, and how 

 would you locate them with 

 reference to the outside of 

 the ovary ? 



Fertilization of the 

 Flower. — The ovules, 

 under certain conditions, 

 become seeds. An expla- 

 nation of these condi- 

 tions may be had if we 

 examine, under the mi- 

 croscope, a very thin 

 section of a pistil, on 

 which pollen has begun 

 to germinate. The cen- 

 tral part of the style is 

 found to be either hollow 

 or composed of a soft 

 tissue through which the 

 pollen tube can easily 

 grow. Upon germina- 

 tion, the pollen tube 

 grows downward through 

 the spongy center of the 

 style, follows the path of least resistance to the locule of the 

 ovary, and there grows into the ovule. It is believed that some 



^ The structural differences in the flower of a monocotyledon and dicotyledon 

 may well be pointed out here. 



hunter's BIOL. — 3 



Fertilization of the ovule. The pollen tubes pass 

 through the stigma and style, finally entering the 

 cavity (locules) of the ovary. 



