INTRODUCTION 25 



with the petals spread widely out. The next 

 morning, however, the flowers appear to wilt; if 

 the day is cool and cloudy they will only partially 

 roll up, but if the day is cloudless and hot they 

 seem completely to collapse. 



The odor of the Evening Primrose is given off 

 to the greatest extent in the evening, when various 

 long-tongued moths are abroad in search of the 

 nectar which is secreted in the long calyx-tubes of 

 the blossoms. Attracted by the odor the moths 

 easily find the bright yellow flowers. They thrust 

 their tongues behind the stamens and stigma to 

 reach the nectar. Some of the stringy, adhesive 

 pollen is thus dusted upon their mouth parts and 

 carried from flower to flower; when it comes in 

 contact with a viscid stigma it adheres to it. 



In this way the moths perform the useful office 

 of cross-pollination, the carrying of pollen from 

 the anthers of one blossom to the stigmas of 

 another. 



Besides the moths which thus visit the blossoms 

 in the evening there are a number of bees and 

 flies that may be found upon the flowers in the 

 daytime; some of these come for nectar and 

 some for pollen. They probably assist in cross- 

 pollination to a considerable extent. 



There are certain bumble-bees, however, which 

 are not useful as visitors to the Evening Prim- 

 rose, for, instead of entering at the mouth of the 



