116 THE STORY OF THE PLANTS. 



female flowers by bringing pollen from the males 

 1 to them with a camel's hair brush. This pro- 

 cess is commonly known as " setting " the 

 f melons. Many other garden flowers have 

 I separate male and female blossoms, which the 

 \ beginner can easily recognise for himself if he 

 takes the trouble to look for them. 



In the instances we have hitherto considered, 

 the male and female blossoms live on the same 

 plant. But the best cross-fertilisation of all is 

 that which is secured where the fathers and 

 I mothers belong to totally distinct plants, a plan 

 J for facilitating which we have already seen in 

 ^the common primrose. Well, now, if any 

 species took to producing all male flowers on 

 one plant, and all females on another, this great 

 end would become absolutely certain, for every 

 blossom would then always be fertilised by the 

 pollen brought from a distinct plant. Many such 

 instances have accordingly been produced in the 

 world around us by natural selection. Only, the 

 two kinds of plants must always grow in one 

 another's neighbourhood. Hemp, for example, 

 is a case of a plant where such an arrangement 

 already exists ; some plants are male only, while 

 some are female. Mistletoe and hops are other 

 well-known instances, which the reader should 

 carefully examine for himself at the proper 

 season. 



All these are fivefold flowers, and I have 

 brought them in here merely because one of 

 the earliest and simplest threefold flowers we 

 are going to consider has also this peculiarity 



