The Flower. 101 



no pistil and hence no ovule, can of course produce no 

 seed. 



150. Pollination (pol-lin-a'-tion) is the access of pol- 

 len (143), to the stigma (144)— the first step in the 

 process of fecundation. During a certain period, the 

 surface of the stigma is moistened by the secretion of a 

 viscid liquid, to which the pollen grains readily ad- 

 here. Fertile pollen grains,* alighting on the stigma 

 of sufficiently near-related plants during this period, 

 undergo a process comparable to germination, in which 

 a slender projection from the pollen cell penetrates the 

 stigma, passes lengthwise through the center of the 

 style and enters the ovule, where fecundation occurs. 



Pollination is not necessarily followed by fecunda- 

 tion. In young plants, and in older plants that are 

 lacking in vigor (9), flowers often fail to produce seed 

 or fruit, even when pistil and stamens appear to be 

 normally developed, and pollination occurs. Pollen is 

 probably more profuse and more potent some seasons 

 than others. 



In some flowers, as in the pea, the stigma is brought 

 into direct contact with the pollen by the elongation of 

 the style, but in most plants the pollen must be trans- 

 ferred to the stigma by some outside influence, as by in- 

 sects, the wind, or gravity. Most flowers which have a 

 showy corolla or calyx, or secret nectar, or yield a fra- 

 grant perfume, depend largely upon the visits of pol- 

 len-loving or nectar-loving insects for pollination. The 

 showy parts and the perfume serve as signboards to 

 direct the wandering insects to the flowers. Pollination 

 is favored by a warm, dry atmosphere. 



• Fertile pollen is pollen that is capable of fecundating female cells 

 of its own species. 



