282 REPRODUCTION 



in many cases have long slender filaments which allow of their 

 easy movement even by gentle breezes : the stigmas are often 

 very large and feathery and specially adapted to catch the floating 

 pollen-grains. 



Insect-pollinated flowers, of which roses, honeysuckle, clover 

 and primrose may be mentioned as examples, usually have 

 brightly-coloured petals or sepals, and are often highly-scented. 

 Nectaries or honey-glands which secrete nectar, a sweet liquid 

 commonly called ' honey,' occur on various parts of the flower. 



Their pollen-grains are less abundant than in wind-pollinated 

 flowers and generally have an ornamented sticky surface which 

 enables them to cling together and to the bodies of insects. The 

 stigmas of such flowers are comparatively small, and when ready 

 for pollination often exude a viscous liquid to which the pollen- 

 grains readily adhere, and in which they germinate freely. 



The insects which visit flowers are mainly beetles, flies, moths, 

 butterflies, and bees. The various tints of flowers, their odour 

 and the nectar which is secreted by them, sei-ve to attract these 

 visitors, and in certain measure enable the latter to distinguish 

 the particular species of plant which they wish to visit. 



Insects feed upon nectar and also to some extent upon pollen, 

 which they obtain in part from wind-pollinated flowers which 

 contain no nectar. 



In their search for a livelihood bees and other insects uncon- 

 sciously render useful service to the plants which they visit by 

 bringing about cross-pollination. 



Where the nectar is exposed or easily accessible, as in 

 most umbelliferous plants and buttercups, a great variety of 

 insects belonging to different families are attracted, and many 

 of them creep about and often merely self-pollinate the flowers. 

 In many cases, however, the nectar is secreted and stored at 

 the base of long, tubular corollas and calyces, or in places other- 

 wise difificult of access, where it can only be reached by insects, 

 such as moths, butterflies, and bees, possessing long proboscides 



