Reproduction 



357 



ing the results and benefits of the process ; but emphasis 

 should be laid upon the union of characters amphimixis 

 thus effected. Reference is made 

 later to the segregation of characters 

 which is conceded to take place. 



Every ovule requires a pollen-grain 

 and a pollen-tube. In fact, for fer- 

 tilization of all the ovules in any 

 plant, many more pollen-grains ger- 

 minate and penetrate the style, since 

 two or more tubes may be directed 

 toward the same ovule. The water- 

 melon may develop more than five 

 hundred seed, so that more than a 

 thousand pollen grains should fall upon 

 a single stigma to insure the maturity 

 of all the seed. 



All the ovules may be fertilized, 

 yet this does not guarantee fruit devel- 

 opment of all. Frequently the plant 

 would be unable to support the weight, 

 or growth demands, resulting from the 

 development of every fruit. 



Unfertilized blossoms are usually 

 the first to fall, but familiar examples 

 are evident on every hand of wild and 

 cultivated plants which shed many 

 fertile blossoms. Correlative growth 

 influences, which are little understood, 

 or an unfavorable environment, may take heavy toll as 

 the young fruit develops ; so that at maturity only a small 



FIG. 100. Carpel of a 

 legume, diagram- 

 matic section at the 

 time of fertilization. 



