SELF-FERTILISED FLOWERS 175 



of the tall leafy green orchis, are so organised as 

 completely to prohibit self-fertilisation. 



The complicated mechanism of the milkweed 

 rigidly exacts cross-fertilisation; and we know that 

 the clover is as firm in the matter — as was proved 

 by the experience of the farmers of Australia, who 

 could get no clover to make seed till bumblebees 

 were imported. 



The jewel-weed, iris, tiumpet-vine, and monkey- 

 flower should be crossed off, since their mechanisms 

 also forbid self-fertilisation. Then, the manv flow- 

 ers whose stamens shed pollen and wither before 

 the stigma is ripe, of which the wild geranium is a 

 type, are practically secure against self-fertilisa- 

 tion ; for, to all intents and purposes, they are stam- 

 inate flowers at one stage and pistillate at another. 



The flowers belonging to the classes so far men- 

 tioned are perpetuated through cross-fertilisation 

 only. 



After them come many flowers which are less 

 strict in their habits, and which permit or even ar- 

 range for self-fertilisation, as a last resort, to avoid 

 extermination. 



In the mountain laurel flower it might easily hap- 

 pen that a few grains of pollen should be thrown 

 upon the stigma, though as a rule the body of the 

 moth visiting the flower is likely to form a shield 



