MENDELISM 



liberated pollen is scattered about, some of it alights on the 

 stigma, and is retained there by the sticky juice (Fig. 2). 

 Very soon the pollen grain begins to shoot out little finger- 

 like processes called "pollen-tubes," which grow down the 



Fig. 2. 



A and B are pollen grains with commencing " pollen tubes." 

 C — Section (vertical) of stigma ; showing two pollen grains resting 

 on the upper surface, with their downward growing tubes. 



whole length of the pistil, until they eventually reach the 

 ovules. The pollen-tube then enters an ovule, and the two 

 bodies (pollen grain and ovule) become blended into one 

 body, and a ripe seed is the result of the union. 



The union of pollen grain with ovule constitutes what is 

 termed " fertilization " : the pollen is said to fertilize the 

 ovule ; and without the addition of the pollen the ovules 

 will not ripen into "seeds." The pollen is the male ele- 

 ment, the ovule is the female element. We may have " self- 

 fertilization," and " cross-fertilization." When pollen fer- 

 tilizes the ovules of its own flowers, we get " self-fertilization," 

 but the pollen of one flower may be carried by such insects 

 as bees, butterflies and moths to another flower, and effect 

 "cross-fertilization." If the pollen from A (Fig. 3) fer- 



