248 ELEMENTS OF SCIENCE 



in the mud which may adhere to their feet. Many 

 curious arrangements exist by which the access of insects 

 to flowers which, as before said, they accidentally fer- 

 tilise by dusting the stigma with pollen is facilitated, 

 and others whereby the approach of noxious creatures is 

 prevented. 



Plants, the pollen of which is only carried accidentally 

 by the wind, may have each of their pollen-grains 

 furnished with a membranous expansion which facili- 

 tates its carriage. 



There is sometimes a curious resemblance between 

 different creatures, which goes by the name of mimicry. 

 Familiar examples of mimicry are clear-winged moths, 

 which may be readily mistaken for bees. One of the 

 most perfect examples of mimicry is displayed by the 

 insect called the "walking leaf," which in form and 

 colour so closely resembles a leaf that it is difficult to 

 find it when amongst real leaves, and thus it escapes 

 its enemies. 



Other creatures, called " bamboo-insects," resemble a 

 stick of bamboo, and this the more because they have 

 the habit of hanging with their long legs stretched out 

 unsymmetrically. 



Certain African species of those plants which are 

 called euphorbias so greatly resemble some American 

 cacti, that it is difficult to believe, when out of flower, 

 that they are not close allies, instead of being plants 

 which belong to widely different groups. 



Very many animals partake of the colour of their 

 usual surroundings. Thus, desert snakes and lizards are 

 generally sand-coloured, while those which inhabit trees 

 are green. 



Actual changes of colour sometimes preserve this 

 harmony. Thus the ptarmigan, the variable hare, the 



