Wi] THE FERTILISATION OF FLOWERS. 4! 
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 thé 
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 Figl e 
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 
