POLLINATION 



133 



212. Staminate catkins of oak. The pistil- 

 late flowers are in the leaf axils, 

 and not shown in this picture. 



flowers are on the same plant, e. g., oak (Fig. 212), beech, 

 chestnut, hazel, walnut, hickory, the plant is monoecious 

 ( " in one house " ) . When 

 they are on different plants 

 (poplar and willow, Fig. 

 213), the plant is dioecious 

 ("in two houses"). Monoe- 

 cious and dioecious plants 

 may be pollinated by wind 

 or insects, or other agents. 

 They are usually wind -polli- 

 nated, although willows are 

 often, if not mostly, insect- 

 pollinated. The Indian corn 

 (Fig. 214) is a monoecious plant. The staminate flowers 

 are in a terminal panicle (tassel). The pistillate flow- 

 ers are in a dense spike (ear), inclosed in a sheath or 

 husk. Each "silk" is a style. Each pistillate flower pro- 

 duces a kernel of corn. Sometimes a few pistillate flowers 



are borne in the tassel and a 

 few staminate flowers on the 

 tip of the ear. 



269. Although most flowers 

 are of such character as to 

 insure or increase the chances 

 of cross -pollination, there are 

 some which absolutely forbid 

 crossing. These flowers are 

 usually borne beneath or on 

 the ground, and they lack 

 showy colors and perfumes. 

 They are known as cleis- 

 togamous flowers (meaning 

 "hidden flowers"). The plant has normal showy flowers 

 which maybe insect -pollinated, and in addition is provided 



213. Catkins of a willow. A staminate 

 flower is shown at s, and a pistil- 

 late flower at p. The staminate 

 and pistillate are on different 

 plants. 



