THE EVOLUTION OF PLANT REPRODUCTION 



73 



An insect, in brushing past the stamen, catches some of the 

 dry pollen on his hairy legs, and flies on in search of nectar; in 

 doing so he may brush off" some pollen on the pistil of the same or 

 another flower. By doing so, he is transporting the male sexual 



Fig. 46. 



MA JURE I MM A TURC 



-Microspores (pollen grains) develop in sacs in the stamens. 



generation to the pistil. This latter organ is a flower part quite 

 difl"erent from anything found in the female cone of the pine. 

 There the sporangia containing the megaspores developed on the 

 surface of the cone scale; but in a flower, the sporangia (ovules) 



OVULES 



LILY ORCHID 



Fig. 47. — ^The ovules in the pistil are sporangia producing megaspores. 



are produced within the tissue of the pistil. Within the ovule (fig. 

 47), the megaspore produces a vestigial female prothallus as well 

 as a functional egg. After pollination has taken place, the pollen 

 grain germinates on the top of the pistil, producing a pollen tube 



