POLLINATION 233 



such corollas with a hole in the tube near the base, made 

 by thieving bees and wasps which thus get at the honey 

 surreptitiously, without 

 paying their tribute of 

 pollen. On the other 

 hand, plants like the car- 

 rion flower, and skunk 461- Head and bill of sword bird 



(Doctmastes ensiferus). 



cabbage seem to practice 



a kind of fraud upon flesh flies by imitating the colors 



and odors of the garbage upon which such creatures feed. 



337. Experiments. An instructive experiment may be 

 made with regard to the color preferences of insects by 

 putting a drop or two of syrup on bits of glass and laying 

 them on paper of different colors in the neighborhood of 

 a beehive or other place frequented by insects, and ob- 

 serving which color seems to attract them most. Similar 

 experiments may be made with perfumes and flavorings. 



338. Color, being a very variable and unstable quality, is 

 of little use in classifying flowers, yet it is interesting to 

 know that all their endless variations of hue are confined 

 approximately within certain limits. Nobody has ever seen 

 a blue rose or a yellow aster, and though the florist's art 

 is constantly narrowing the application of this law, it still 

 remains true that in a state of nature certain colors seem 

 to be associated together in the floral art gamut. Yellow 

 is considered by botanists the simplest and most primitive 

 color in flowers, and blue the latest and most highly 

 evolved. Yellow, white, and purple, in the order named, 

 are the commonest flower colors in nature ; blue the rarest. 



PRACTICAL QUESTIONS 



1. Why do the flowers of oak, willow, and other wind-fertilized 

 plants generally appear before the leaves? (332.) 



2. Can you account for the "showers of sulphur" frequently 

 reported in the newspapers? (332.) 



3. Do you see any connection between the feathery stigmas of 

 most grasses and their mode of pollination? (332.) 



