174 



ESSENTIALS OF BOTANY 



or by appendages.^ Those flowers which have one or 

 more sepals or petals prolonged into spurs, like the nastur- 

 tium and the columbine, are inaccessible to most insects 

 except those which have a tongue or a sucking-tube long 



.^ 



Fig. 130. A Sphinx Moth with a Long Suoking-Tube. 



enough to reach to the nectary at the bottom of the spur. 

 The large sphinx moth, shown in Fig. 130, which is a com- 

 mon visitor to the flowers of the evening primrose, is an 

 example of an insect especially adapted to reach deep 

 into long tubular flowers. 



207. Bird-Pollinated Flowers. — Some flowers with very 

 long tubular corollas depend entirely upon birds to carry 

 their pollen for them. Among garden flowers the gladi- 

 olus, the scarlet salvia, and the trumpet honeysuckle are 

 largely dependent upon humming-birds for their pollina- 

 tion. The wild balsam or jewel-weed and the trumpet- 

 creeper are also favorite flowers of the humming-bird. 



208. Prevention of Self -Fertilization. — Dioecious flowers 

 are of course quite incapable of self-pollination. 



1 On protection of pollen, see Kerner and Oliver, Vol. II, pp. 95-109. 



