On Flowers and Insects. 153 



visited during the day by humble bees, this is not 

 the case with the Primrose, which appears to be 

 fertilised almost exclusively by moths. 



The genus Lythrum affords a still more complex 

 case, for here we have three forms of flowers. The 

 stamens are in two groups : in the one form the 

 pistil projects beyond either of them ; in the second 

 form it is shorter than either of them, and in the 

 third it is intermediate in length, so that the stigma 

 lies between the two sets of anthers. 



8. Although flowers present us with these beau- 

 tiful and complex contrivances, whereby the transfer 

 of pollen from flower to flower is provided for, and 

 waste is prevented, yet they appear to be imperfect, 

 or at least not yet perfect in their adaptations. 

 Many small insects obtain access to flowers and 

 rob them of their contents. The Dwarf Mallow 

 can be, and often is, sucked by bees from the out- 

 side, in which case the flower derives no advantage 

 from the visit of the insect. In the Lucerne, also, 

 insects can suck the honey without effecting fertili- 

 sation, 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 

 M tiller has observed that in some plants which are 

 exclusively fertilised by night-flying insects, many 

 of the flowers nevertheless open in the day, and 

 consequently remain sterile. It is of course possible 

 that these cases may be explained away ; neverthe- 

 less, as both insects and flowers are continually 



