THE ANGIOSPERMAE 



1263 



monopoly. As they have only themselves to look after, they are not so 

 particular about the quality of the nectar they obtain, and like flies may be 

 satisfied with nectar that would not attract the Honey Bee. 



Butterfly and moth flowers are easily noticed on account of their visitors. 

 Among them are Dianthiis, Phlox, Buddleia, Glohiilaria, and some species 

 of Liliiiin, e.g., L. philadelphicum (Fig. 1206). Other Lilies, like L. cana- 

 detise, are bee flowers and it is noteworthy that the latter have fixed, not 

 versatile anthers. The versatile anthers are better suited to contact wdth 

 the large, beating wings of the Butterfly. 



A striking case of close association between a flower and a particular 

 type of insect is that of the Red Clover cultivated in New Zealand. When 

 the plant was first introduced there, none of the local insects would visit 

 it and the plants remained sterile. To get seed it was necessary to import 

 English Humble Bees who fek at home with the Clover flowers and long 

 remained faithful to it in 

 spite of the competing 

 attractions of the native 

 flora. 



This mutual depend- 

 ence may reach a stage 

 where neither plant nor 

 insect can thrive without 

 the other. The case of 



the Fig will be described 



later. Two other famous 



examples are those of 



Yucca and of Silene 



nutans. 



The flowers of all 



species of Yucca dLXthomt 



in large panicles and as 



they are white they are 



easily visible at night. 



The fresh buds open at 



sundown and the flowers 



form pendent bells (Fig. 



1207). They are visited by 



a small yellowish-white 



moth named Pronuba 



yuccasella, the females of 



which creep into the 



flowers and collect pollen 



from the small anthers, 



which are borne on large, 



woolly filaments. This 



pollen the insect rolls up 

 H 



M 



Fig. 1 207. — Yucca ichipplei. A, Part of a flowering shoot. B, 

 Flower open and ready for pollination. C, Female of 

 Pronuba yuccasella placing a ball of pollen on the stig- 

 mas. {Partly after Kerner.) 



