FLOWERS AND THEIR USES 



269 



spines or warts; thus they are hkely to stick to insects' 

 bodies and so to be carried about. The stigmas, too, are 

 commonly rough and sticky. Insect-pollinated plants have 

 various ways of advertising their presence to the insects 

 whose assistance is needed. Many of them have large, 

 brightly colored or white flowers. The plants that we raise 

 for the beauty of their flowers are insect-pollinated ; the size 



Fig. 158. — Salvia glutinosa, showing how cross-pollination is assured. 

 Ay a stamen; the short upright column (/) is the filament; c, c, the long 

 connective, bearing the anther at its upper end. B, a lengthwise section 

 of a young flower, showing the anther in its natural position. C, the same, 

 the anther having been pushed down by a bee pressing on the lower part 

 of the connective. D, a bee visiting a young flower ; the anthers have been 

 pushed down and are touching the bee's back. E, a bee visiting an older 

 flower whose poUen has been shed ; the style has now grown long and hangs 

 down so as to touch the bee's back at the same place at which it was touched 

 by the anthers of the younger flower. After Kerner. 



and color of the flowers have come about, not because they 

 are beautiful, but because such flowers attract insects and 

 in this way are useful to the plant. We have selected the 

 plants for cultivation because the same things that make 

 their flowers attractive to insects are also pleasing to us. 



However, the flowers of many cultivated plants have 

 been made much larger and more showy by breeding than 

 they originally were. Our large double roses and carnations, 



