The Angiosperms 177 



metry is bilateral, the flower often being two-lipped, 

 as in the sage and other "labiate" flowers (Fig. 

 19, E, F). This " zygomorphy " is frequently asso- 

 ciated with a reduction in the number of stamens, 

 as in the fox-glove or snap-dragon, where instead 

 of the five stamens which would correspond to the 

 number of petals, there are but four. Sometimes a 

 rudiment of the fifth stamen is visible, as in the 

 Pentstemon. Zygomorphy does not necessarily in- 

 volve a reduction of the stamens, the sweet-pea, for 

 instance, having ten stamens, or twice the number of 

 the petals. 



Perfume and Color as Lures for Insects. The 

 inconspicuous flowers of the Apetalse are usually 

 destitute of perfume, which is so marked in so many 

 flowers. There seems no good reason to doubt that 

 the presence of strong odors, agreeable or other- 

 wise, is associated with the visits of insects which 

 are attracted to the flower both for the sake of the 

 pollen, which was probably their first object in visit- 

 ing the flowers, and for the sake of the nectar which 

 is secreted by many of them. The gay colors of 

 the petals and sometimes of the other parts of the 

 flowers, or inflorescence, e.g., the stamens in Euca- 

 lyptus, the sepals in the Clematis, or the accessory 

 bracts in the arum, or dogwood, are usually also re- 

 garded as a means of attracting insects or birds. 



There has been lately a tendency to minimize the 

 importance of insects as the agents of cross-pollina- 

 tion, and the significance of the coloring of the flow- 



