284 



FLOWERS 



monoecious. (Study Figure 104.) Plants which bear stami- 



nate and pistillate flowers 

 on different individuals are 

 called dioecious. (The word 

 means two households.) 

 Many common trees are 

 dioecious. The box elder, 

 the poplar, and the willow 

 are examples. (See Figures 

 105 and 106.) It is evident 

 that only the pistillate box 

 elders or poplars can pro- 

 duce fruit, and this fruit will 

 produce good seed only if 

 staminate trees are in the 

 same vicinity with pistillate 

 ones. 



There are some plants, 

 some kinds of maple trees, 

 for example, which pro- 

 duce both monoclinous and 

 diclinous flowers. Such 

 plants are called polyg- 

 amous. 



Fig. 104. — A flowering twig of hazel, a 

 shrub which has monoecious, wind-pol- 

 linated flowers. Note that the stami- 

 nate flowers are lower than the pistillate 

 ones ; this tends to prevent pollen from 

 falling on stigmas of the same plant. 

 The catkins sway in the breeze, the 

 pollen grains often being blown from 

 them in little clouds. The uppermost 

 small picture shows a single pistillate 

 flower; the one below it, a single 

 staminate flower. 



C. Kinds of Perianths. 

 — It is believed that plants 

 with perianths came from 

 plants without them ; that 

 is, naked flowers are more 

 primitive than flowers with perianths. The more primitive 

 perianths appear to be those whose parts are spirally ar- 



