96 GENERAL CONSIDERATIONS 



collectively the calyx, are for protection. They are 

 usually green in color like the leaves; they serve to 

 wraj) up and protect the other organs while they 

 are young. The next set, called the corolla, are for 

 display. They also serve to protect the more im- 

 portant organs within, but their chief function 

 seems to be to attract insects. The central essential 

 organs which are so carefully wrapped up by the calyx 

 and corolla also are of two kinds, the stamens and 

 pistils. The stamens produce a considerable quan- 

 tity of a yellowish powder called the pollen. This 

 represents the male element. At the top of the 

 pistil is a moist sticky surface called the stigma. 

 When a pollen grain falls on this, it adheres to it 

 and begins to grow, sending out a slender micro- 

 scopic tube which penetrates the tissues of the pistil, 

 finally reaching the enlarged base called the ovary, 

 where the egg cell or female cell is located. The 

 nucleus of the pollen grain passes down through the 

 tube, enters the egg cell, and unites with its nucleus, 

 — thus effecting fecundation. The fecundated egg 

 cell now begins to divide and grows into the rudi- 

 mentary plantlet called the embryo. This with its 

 surrounding supply of reserve food material and 

 its various protective coatings constitutes the seed 

 which, when planted under favorable conditions, will 

 germinate and grow into a new plant like the one 

 from which it sprung. 



It seems to be almost a universal rule in nature 

 that the young will be more vigorous when the male 

 and female cells from which they spring are not too 

 closely related. We therefore find some kinds of 



