VARIATIONS IN STRUCTURE 



283 



is quite sure to blow or fall upon 

 the silk. A pollen tube must 

 grow down each thread of the 

 silk if all the ovaries are to be- 

 come well developed grains of 

 corn. If the days when the 

 pollen is ripe are rainy, the corn 

 crop is sure to be injured there- 

 by. Dry days are needed when 

 the pollen is flying. Rain 

 makes wind-pollination very un- 

 certain. The ovary of corn be- 

 comes completely filled by the 

 one seed which develops within 

 it. Thus, strictly speaking, a 

 grain of corn is not a seed ; it 

 is rather a fruit completely filled 

 by the one seed which it con- 

 tains. 



Plants with diclinous flowers 

 bear these flowers in two ways. 

 One way is to bear both stam- 

 inate and pistillate flowers 

 upon the same individual; the 

 other is to bear the staminate 

 flowers upon some individuals 

 and the pistillate flowers upon 

 others. Plants bearing both 

 kinds of flowers upon the same FlG I03 ._ The end of a young 



individual are Called monceCWUS. ear of corn, the silk being exposed 



(The word means one household.} at l j e ^ Note that a ^ read 



of the silk runs to each of the 



Cat-tail and corn are both young grains. 



