10 Flowers and their Unbidden Guests. 



not less important function is to attract by the secre- 

 tion of nectar, by odours perceptible afar, and by ; 

 colours contrasting vividly with the green of the leaves, 

 such insects as may carry the pollen from one flower 

 to another, and so bring about allogamy. Finally, the 

 perianth has stiU another function, namely, to protect 

 the nectar, which is not always secreted only at the 

 base of the perianth, but often also in hollows of 

 different parts of the androecium or gynaecium, or by ; 

 peculiar epiblastemes, sometimes of one sometimes of 

 another of the floral whorls, or of the bottom of the 

 flower, and which must be secured not only against 

 injurious weather influences, but specially against the 

 plundering of such insects as would visit the flower 

 without conferring any advantage. Again the divisions 

 of the perianth, in a more or less changed form, often act 

 as a protection to the young fruits, which develop under 

 their shelter. Often too they conduce to the dispersal 

 of the seed, as when they form dry and membranous 

 coverings which offer a relatively large surface to the 

 wind {Trifolium hadium), or when they adhere to 

 roving animals either by viscidity (Plumbago, Linncea)} 

 or by booklets (Marrubium), or when they are converted 

 into fleshy pericarps which serve as food for animals. 



^ [The fruit of Zinncea, lorealis, as also the calyx of several 

 species of Plumhago (P. micrantJia, and rosea) are covered with 

 glandular hairs. On the whole subject of special appliances for 

 dispersal of seeds, consult the monograph of F. Hildebrand, Dii 

 Verbreitungsmittel der Pflanzen. Leipzig, 1873. — Editor.] 



