POLLINATION 53 
place ; but many botanists*have tried artificial self-pollination 
of primroses, and have found that when seed is thus produced 
it is not so productive as when the flowers have been cross- 
____ pollinated. 
Agents Flowers are usually cross-pollinated by means 
effecting ; . 
Cross- Of _wind or insects ; the former are called anemo- 
Pollination. philous (Gk. anemos=wind), the latter entomo- 
philous (Gk. entoma = insects). 
Anemophilous flowers are often small and inconspicuous, 
never brightly coloured. They are plentifully provided with 
pollen, which is powdery and readily shaken out of the flower 
owing to the fact that the stamens have long filaments. The 
stigmas are olten branched and hairy or tuftlike, as in the 
Hazel and Grasses. As a rule, wind-pollinated plants flower 
early in spring. 
Kntomophilous flowers generally have nectaries, and by their 
scent attract insects. They are usually brightly coloured, as 
Sprengel first pointed out, and consequently very conspicuous ; 
often they are irregular, the irregularity—as, for instance, the — 
lower lip of the Dead-nettle, the “wings” of the Sweet Pea, 
etc.—being of assistance to the insect. 
Many flowers, too, have hairs or markings 
of various kinds, which serve to direct the 
insect to the nectary. The pollen grains 
of entomophilous flowers are sticky, not 
powdery, and the stigmas are usually 
smaller than in the case of wind-pollinated 
flowers. 
Nectaries may be found in 
almost any part of the flower. 
In the Buttercup, at the base of each petal Ee ee 
alittle scale may be seen ; the nectary lies np Gynacrum ox 
just under this. In the Wallflower, the  ‘’S¢2#L0W=R. 
nectaries are little green swellings at the ae ae 
base of the two short stamens (Fig. 64). 
In the Violet, two of the stamens have appendages which make 
honey, that is collected in the spur of the corolla into which the 
Nectaries. 

