124 



PKACTICAL BOTANY 



been seen to be frequented by 100 kinds of insects. 1 The sta- 

 tistics of visitors to the flowers of yarrow, Canada thistle, and 

 the willows are fully as remarkable. 



117. Attractions offered by insect-pollinated flowers. Insects 

 are led to visit flowers for the sake of procuring food. This is 

 usually either pollen as in the flowers of many species of 



meadow rue, Clematis, Anemone, 

 poppy, rose, Spiraea, and St- 

 John's-wort or both pollen 

 and nectar, as in most kinds 

 of conspicuous flowers. 



Nectar is usually secreted 

 by nectar glands, small organs 

 which are often to be found 

 near the base of the flower, 

 as in buckwheat (Fig. 114). 

 Sometimes the nectar remains 

 on the surfaces of the glands, 

 sometimes it trickles down into 

 the bottom of the flower, and 

 sometimes as in the columbine and the honeysuckle it 

 is stored in pouches called nectaries, situated at the bases of 

 separate petals or at the bottom of the sympetalous corolla. 



Honey is nectar which has been swallowed by the bee and, 

 by partial digestion in its crop, has undergone slight chemical 

 changes. 



118. Odors of flowers as attractions to insects. It is evident 

 from familiar facts that many insects have an acute sense of 

 smell. The way in which flies are attracted by decaying meat 

 or fish, and bees and wasps by a cider press at work, or by 

 fruit-preserving operations, is a matter of common observa- 

 tion. A single cluster of carrion-scented flowers has been 

 known to attract carrion flies and dung beetles from a distance 

 of hundreds of yards. Some flowers such as those of the 



FIG. 114. Flower of buckwheat 



Lengthwise section, showing nectar 

 glands n. Five anthers are discharg- 

 ing pollen ; the other three here shown 

 are not quite mature. After H. Miiller 



1 See Knuth-Davis, Handbook of Flower Pollination, Vol, II. Clarendon 

 Press, Oxford. 



