io COLOUR, SCENT, AND HONEY. [CHAP. 



The transference of the pollen from one flower to 

 another is, as already mentioned, effected principally 

 either by the wind or by insects, though in some cases 

 it is effected by other agencies, as for instance, by 

 birds, or by water. For instance, in the curious Val- 

 lisneria spiralis (Fig. 36) the female flowers are 

 situated on long stalks which are spirally twisted, 

 and grow very rapidly, so that even if the level of 

 the water alters, provided this be within certain 

 limits, the flowers float on the surface. The male 

 flowers on the contrary are minute and sessile, but 

 when mature they detach themselves from the plant, 

 rise to the surface, and float about freely like little 

 boats among the female flowers. 



Wind-fertilised flowers as a rule have no colour, 

 emit no scent, produce no honey, and are symmetri- 

 cal in form. Colour, scent, and honey are the three 

 characteristics by which insects are attracted to 

 flowers. 



As already observed, wind-fertilised flowers gene- 

 rally produce much more pollen than those which 

 are fertilised by insects. This is necessary, because 

 it is obvious that the chances against any given pollen 

 grain reaching the stigma are much greater in the one 

 case than in the other. 



Again, it is an advantage to wind-fertilised plants 

 to flower early in the spring before the leaves are out, 

 because the latter would catch much of the pollen 

 and thus interfere with its access to the stigma. 

 In these plants the pollen is less adherent, so that 

 it can easily be blown away by the wind, which 

 would be a disadvantage in most plants which are 



