136 THE STOKY OF THE PLANTS. 



numerous devices occur to prevent self-fertili- 

 sation. 



You must not suppose, again, that the wind- 

 fertilised plants form a group by themselves, 

 distinct in origin from the insect-fertilised, as 

 Uhe three-petalled group is distinct from the 

 five-petalled. On the contrary, wind-fertilised 

 , kinds are found abundantly in both great 

 ^groups ; it is a matter of habit ; so much so that 

 * sometimes a type has taken first to insect-fertili- 

 sation and then to wind-fertilisation, with com- 

 paratively slight differences in its external 

 appearance. Closely related plants often differ 

 immensely in their marriage customs ; each has 

 varied in the way that best suited itself, accord- 

 ing as insects or breezes happened to serve it 

 most readily. In my own opinion all wind- 

 fertilised plants are the descendants of insect- 

 fertilised ancestors ; but I do not know whether 

 in this belief my ideas would be accepted by 

 most modern botanists. 



As a first example of wind-fertilised flowers, 

 I will take the common dog's mercury, a well- 

 known English wayside flower, frequent in 

 copses and hedgerows, and one of the very 

 earliest to blossom in spring. In this species 

 the males and females grow on senarate plants. 

 They have each a calyx of three sepals (two 

 more being suppressed, for they belong by 

 origin to the fivefold division). The males have 

 ten or twelve stamens apiece, which hang out 

 freely with long stalks to the breeze. The 

 females have a two-chambered ovary, with 

 rudiments or relics of some two or three 



