426 



HUTCHINSON'S POPULAR BOTANY 



which is very attractive to those insects. They flock to the banqueting- 

 house in great numbers, and if they have brought pollen from other arums, 

 pollinate the stigmas, which thereupon wither. The little visitors at the 

 same time receive payment for their services in nectar, of which each stigma 



yields a single drop. 

 Afterwards the anthers 

 shed their pollen, which 

 falls, upon the chamber 

 floor, and the flies get 

 well dusted. Their ser- 

 vices being now required 

 by the plant no longer, 

 the palisade of hairs 

 shrivels up, and the 

 prisoners are set free. 



The imprisonment of 

 bidden guests is not how- 

 ever a frequent occur- 

 rence among plants. It 

 is by no means a usual 

 thing for the front door 

 to be locked on a visitor 

 when he enters a flower. 

 Nevertheless, the treat- 

 ment which these uncon- 

 scious benefactors re- 

 ceive is often sufficiently 

 rough and unhandsome ; 

 and perhaps no plants 

 are greater offenders in 

 this respect than those 

 rajahs of the Vegetable 

 World, the Orchids, to 

 which we shall refer 

 again shortly. For the 

 present let us examine 

 one or two of our com- 

 mon flowers, in which 

 the contrivances for 

 securing cross-fertilization, though exceedingly curious, are simpler than 

 those of the flowers named. 



We may start with what has been aptly called the bt^ush and piston 

 mechanism of the cultivated Pea (Pisum sativum), which supplies a type 

 rather common, though with varying modifications, among papilionaceous 



Photo by] 



[E. Step. 



FIG. 529. BUTTERFLY ORCHIS (Habenaria bifolia). 



The greenish -white flowers are specially adapted for pollination by moths, and 

 are very fragrant at night, when they show up conspicuously. 



