44 THE ORIGIN OF FLO WERS. [chap. ii. 



their contents. Malva rotundifolia can be, and often 

 is, sucked by bees from the outside, in which case the 

 flower derives no advantage from the visit of the 

 insect. In Medicago sativa, also, insects can suck the 

 honey without effecting fertilisation, and the same 

 flower continues to secrete honey after fertilisation 

 has taken place, and when, apparently, it can no 

 longer be of any use. Fritz MuUer has observed that 

 though Posoqueria fragrans is exclusively fertilised by 

 night-flying insects, many of the flowers open in the 

 day, and consequently remain sterile. It is of course 

 possible that these cases may be explained away ; 

 nevertheless, as both insects and flowers are con- 

 tinually altering in their structure, and in their geo- 

 graphical distribution, we should naturally expect to 

 find such instances. Water continually tends to find 

 its own level ; animals and plants as constantly tend 

 to adapt themselves to their conditions. For it is 

 obvious that any blossom which differed from the 

 form and size best adapted to secure the due trans- 

 ference of the pollen would be less Ukely to be 

 fertilised than others ; while on the other hand, those 

 richest «i honey, sweetest, and most conspicuous, 

 would most surely attract the attention and secure the 

 visits of insects ; and thus, just as our gardeners, by 

 selecting seed from the most beautiful varieties, have 

 done so much to adorn our gardens, so have insects, 

 by fertilising the largest and most brilliant flowers, 

 contributed unconsciously, but not less effectually, to 

 the beauty of our woods and fields.^ 



^ I have treated the subject of these chapters at greater length in a 

 special book on Flowers and Insects, forming one of the present series. 



