98 CO UN CLOUT'S CALENDAR. 



they arc groups whose ancestors have undergone much 

 variation, so that at last a tendency to vary easily has 

 become hereditary with them all. Of such families, the 

 orchids and the snapdragons are the most conspicuous ; 

 and the\- differ so much and so quaintly among them- 

 selves that one can hardly avoid involuntarily attributing 

 to them a sort of human spontaneity and deliberate 

 design. Some of them mimic the forms and colours of 

 msects ; others assume the most fantastic shapes and 

 hues — apparently out of pure wantonness, but really in 

 order to ensure fertilisation by the oddest and most 

 improbable methods. The common snapdragon, for 

 example, has the mouth of its blossom tightly closed by 

 a projecting palate, .«o as to exclude all insects exce})t 

 the correlated kind of bee, whose weight as he lights on 

 the lip suffices to press down the door and give him 

 access to the scaled tube, with its nectar secreted in a 

 little pouch at the far end. As soon as he flies away the 

 palate snaps back again, and closes the entrance once 

 more till another bee presents himself on the threshold. 

 The yellow-rattle has just as complicated an arrange- 

 ment on a smaller scale, with an arched and flattened 

 upper lip, flanked by two purple-spotted wings, as well 

 as a lobed lower lip, deeply divided into three distinct 

 segments. The flowers are minutely arranged for fer- 

 tilisation by bees ; and the insect is obliged to thrust 

 his proboscis between the closely locked and hairy 

 stamens in order to get at the honey. In doing so, he 

 necessarily shakes out the pollen, which he carries away 

 with him on his head to the next blossom. 



In a very plastic and variable family such as this, 

 the general plasticity seems to affect every part (jf the 



