296 THE STORY-BOOK OF SCIENCE 



of seeds ready to germinate and produce new plants. 

 Do not question me further about these wonderful 

 things concerning which even the keenest observer 

 ceases to see clearly. God only, the wisest of beings, 

 knows how a grain of pollen can give birth to some- 

 thing that was not before, and can cause the ovary 

 to feel the stirring of the vital principle. 



"I will- tell you now how we know that the falling 

 of the pollen on to the stigma is indispensable to the 

 development of the ovary into fruit. 



"Most flowers have both stamens and pistils. All 

 those we have just looked at are in that class. But 

 there are plants that have some flowers with stamens 

 and others with pistils. Sometimes the flowers with 

 stamens only and those with pistils only are found 

 on the same plant; sometimes they are found on 

 separate plants. 



"Did I not fear to overcharge your memory, I 

 would tell you that plants having flowers with sta- 

 mens only and flowers with pistils only on the same 

 plant are called monoecious plants. This expression 

 means ' living in one house/ In a word, the flowers 

 with stamens and those with pistils live together in 

 the same house, since they are found on the same 

 plant. The pumpkin, cucumber, melon, are monoe- 

 cious plants. 



"Vegetables whose flowers with stamens and 

 flowers with pistils are found on different plants are 

 termed dioecious ; that is to say, plants with a double 

 house. By this is meant that the ovary and pollen 

 are not found in the same plant. The locust, date, 

 and hemp are dioecious. 



