120 



THE FLOWERING PLANT. 



the outer ones irregular and much larger than in the inner 

 ones. 



The most closely related flowers often differ remarkably in 

 character, and this is correlated with differences in pollination. 

 Compare, for instance, the common mallow (Malva sylvestris) 

 and the dwarf mallow (M. rotundi folia). The flower of the former 

 is much the larger, and the numerous stigmas form a tuft above 

 the ends of the monad elphous stamens (cf. p. 95). It is insect- 

 pollinated. The latter has much smaller flowers, and the stigmas 

 and stamens intertwine, favouring self-pollination. A similar 

 pair is found in the large-flowered, proterandrous rose-bay willow 

 herb (Epilobium angustifolium), and the small-flowered willow 

 herb (E. parviflorum), the stamens and stigmas of which mature 

 simultaneously. The following table 1 compares, in this connec- 

 tion, four of our native wild geraniums. 



Monocotyledons are remarkable from the fact that, although 

 they include some of the minutest wind-pollinated forms (sedges, 

 grasses, and rushes), yet, on the other hand, many of the most 

 conspicuous flowers are found among them. Not only is the 

 calyx frequently as bright as the corolla, e.g., in lily, tulip, and 

 hyacinth, but also stamens may become petaloid, as in orchids 

 (cf. p. 88), and the three styles of iris are in the same condition. 

 Their bracts also are frequently petaloid, as in many orchids and 

 hyacinth, while in some exotic arums the enlarged spathe plays 

 the part of a corolla. In many arums, too, the fleshy axis of the 

 sj>adix compensates for the lack of perianth. 



Odour. — This varies according to the visitors required. Fra- 

 grant flowers attract bees, butterflies, moths, and higher insects 

 generally, while more rarely foetid odours are given out with the 

 view of enticing flies. Many flowers which to us appear scentless 

 are probably not so to insects, which seem to be gifted with 

 unusually keen powers of smell. There can be no doubt, for 



1 Modified from Lubbock. 



