FLOWERS 



45 



(3) The corolla is often entirely lacking. It would only be in the 

 way in flowers that are dependent upon the wind to carry pollen. 

 Imperfect Flowers. — Some flowers, the wind-pollinated ones 

 in particular, are imperfect. The plants bear flowers that lack 

 either stamens or pistils. In such plants, cross-pollination must 

 of necessity follow. If the staminate flowers (those which con- 

 tain only stamens) are developed on one plant only, and the 

 pistillate (those which bear only pistils) on another, as in the 

 willow, we call the plant dioecious. 

 Try to make a list of all the trees 

 and grasses in your neighborhood 

 that are dioecious. 



Other plants bear staminate and 

 pistillate flowers on the same plant. 

 In this case they are said to be mo- 

 noecious. The oak, hickoiy, beech, 

 birch, walnut, and chestnut are fa- 

 miliar examples. 



The pine tree is another example 

 of monoecious tree; the male or staminate flowers appear in tiny 

 clusters called catkins, the female or pistillate flowers coming a 

 little later as tiny cones, which in most species of pines take 

 nearly two years to mature into seeds. 



Water Pollination. — An unusual method of pollination is found 

 in those plants which live almost entirely under the water. In eel- 

 grass the pistillate flowers are attached to long slender stalks and 

 float on the surface of the water. The staminate flowers, when ripe, 

 break away from their submerged stems and float to the surface. 

 If these float under a pistillate flower, the protruding ends of the 

 pistils catch and retain some of the pollen from the staminate 

 flower. Thus fertilization follows. After pollination, the stalk of 

 the pistillate flower coils up in a spiral and draws the flower under 

 the surface of the water, so that the seeds may ripen in security. 

 Summary. — If we now collect our observations upon flowers 

 with a view to making a summary of the different devices flowers 

 have assumed to secure cross-pollination, we find that they are as 

 follows: — 



Imperfect flowers of the squash, the 

 corolla removed. Pistillate flower 

 at the left. 



