in.] THE FERTILISATION OF FLOWERS. 41 



depend upon the honey for their fertilisation are 

 specially constructed to protect it. The honey is 

 generally so situated in flowers that to get at it the 

 insect is bound to push itself against the anthers, and 

 when it retires it takes away some of the pollen 

 on its body or head. The stigmas and anthers are 

 usually so placed that on visiting the next flower the 

 pollen on the insect comes into contact with the 

 stigma, and is detached. 



In some cases the stamens and stigmas do not 

 ripen at the same time, so that it is impossible for 

 the plant to be self-fertilised. This is the case with 

 the common Arum, in which the stigmas come to 

 maturity before the anthers. Any one 

 acquainted with the flowers of this plant 

 and few persons are not will under- 

 stand that it is impossible for the pollen 

 to be blown out of the flower after it has 

 been shed by the anthers ; and though, 

 from their being placed above the stigmas, 

 it would seem an easy matter for self- 

 fertilisation to take place, this is prevented 

 by the stigmas maturing before the pollen FIG. 47 . 

 is ripe; so that if it is to be fertilised at 

 all, it must be by pollen being brought from a plant 

 which has flowered a little earlier, and in which the 

 stigmas have passed maturity. Just above the band 

 of anthers (A) are a number of hairs (H) pointing 

 downwards. Small insects in quest of honey easily 

 pass these hairs and reach the bottom, but on wish- 

 ing to return, these same hairs, from their direction, 

 form an effectual barrier, and the insects remain 



