T4 THE PRINCIPLES OP AGRICULTURE. 



The essential parts of a flower are the central, or in- 

 terior oro-ans, by which the seeds are formed. These are 

 generally siirronnded by floral envelopes, called the cah/x 

 and the coroJla, whose individual leaves, the sepaJ.s and 

 2)etals, give the flower its beauty. 



The central organs are of two kinds, called 7>/s'///-'^ and 

 stamens. 



The pistils contain germs from which seeds are formed, 

 and the stamens produce a fine dust, generally of a yel- 

 low color, caWed j^oUeu. 



This pollen, falling upon the ])istils, fertilizes them, 

 and starts the formation of seeds. 



Usually both stamens and })istils grow upon the same 

 plant, aud near each other in the same lluwer. In some 

 varieties, however, the pistils are Ijorne \\\nm one ])lant 

 and the stamens upon another. This is true of some 

 varieties of strawberries, and of hop and hem}) plants. 



On account of this peculiarity, it is necessary, in culti- 

 vating these crops, to mix plants of both kinds. 



Sometimes the pistils are borne upon one part of a 

 plant, and the stamens ujxin another. An example of 

 this is seen in Indian corn. The pollen produced u])on 

 the tassel falls ui)on the silk, which is connected with 

 the pistils within tlie ear. 



Pollen dust is ])roduced l)y some plants in large rpian- 

 tities, and is carried long distances by the wind. This, 

 falling upon different plants of the same species, causes 

 a mixture. 



By a transfer of pollen dust in this way, an almost 

 endless variety of some species of plants is obtaiued. 

 A green variety of scpuishes growing beside a yellow 

 variety yields a variety partly gi-een and ])artly yellow. 

 Grains of pollen dust, carried by the wind from one corn- 



