INSECTS AND FLOWERS 217 



calyx. In flowers of the lily type — tulips, orchids, irises, 

 &c. — the parts of the two whorls (representing the calyx 

 and the corolla) are usually all coloured ; and botanists 

 call the separate parts leaves and the whole structure a 

 'perianth. When the parts of any whorl are all alike 

 in shape, size and arrangement, the whole is said to 

 be regular ; but when one or more parts are in any 

 way different from the rest, the whorl is irregular — 

 these terms being usually applied to the whole flower. 

 Thus, while the buttercup, wild rose and primrose are 

 regular flowers, the pea, white dead-nettle and flgwort are 

 irregular. Not infrequently, a flower is furnished with 

 special glands, or nectaries. These are found exactly 

 where the proboscis of an insect which is adapted for the 

 purpose can reach them. " In regular flowers " (writes the 

 llev. G. Henslow), "which can be approached from all 

 points of the compass, the rule is that the nectar is 

 secreted all round the base of the flower, or by every 

 petal, &c., as the case may be ; but in irregular flowers, 

 which are almost invariably situated close to the stem, so 

 that they can be visited on one side only, the usually 

 single gland is just where the proboscis can best reach it, 

 and nowhere else." 



Pollination consists in the transfer of pollen from the 

 anthers to the stigma of the pistil. In this way fertilisa- 

 tion is effected, the seeds are " set," and the plant becomes 

 fruitful. Some flowers, however, do not combine the sexes 

 in one bloom ; they are wholly male, or wholly female. In 

 such cases a transfer of pollen by some agency external to 

 the plant is clearly indispensable ; while there are many 

 bisexual flowers in which self-pollination is equally impos- 

 sible, either on account of some structural disability, or 

 because the anthers and stigma do not ripen at the same 

 time. These points will become clearer as we proceed, 



