FLORAL CLASSES 357 



B', Inflorescences with concealed nectar, especially 

 characteristic of the Compositae. The only reason for 

 separating this from the previous class is the flower-like 

 appearance of the infloresence, which acts as a single flower 

 so far as attraction is concerned. 



H, Hymenoptera flowers, visited almost exclusively by 

 bees. Here we have a class in which specialised structure 

 permits the visits of only one particular insect or of a limited 

 group. In some the nectar is so deeply placed that only 

 an insect with a very long tongue can reach it, as in the red 

 clover, where the nectar, 9 mm. from the mouth of the 

 flower, is available only to the humble bee. In others only a 

 heavy insect can open the flower, as in the snapdragon or 

 broom. In markedly zygomorphic flowers like the sage, 

 monkshood, violets, snapdragon, broom, and orchids, a 

 convenient landing stage for the bee is combined with 

 deeply concealed nectar at the base of a long corolla tube, or 

 in special spurs. Where such flowers have wide tubes the 

 access of small flies may be prevented by hairs, scales, etc. 



F, Lepidoptera flowers have the nectar deeply concealed 

 in narrow tubes or spurs. They are less massive than bee 

 flowers, and often do not have landing stages, for the butter- 

 fly and moth continue fluttering while sucking. They are 

 frequently marked by a peculiar aromatic scent, the quality 

 of which may best be indicated by reference to the scent of 

 the clove pink. To the same class belong the flowers 

 pollinated by night moths, such as the night-scented stock, 

 the honeysuckle, and the Nottingham catchfly. They are 

 characterised by their stronger fragrance in the evening, 

 and by pale tints easily visible in the twilight. The famous 

 example of the Madagascar orchid, Angrcecum sesqutpedak, 

 may be mentioned (Fig. 49). It has a spur nearly a foot 

 long in which the nectar is produced. On the strength of 

 the existence of this flower, Wallace, in his " Essays on 

 Natural Selection," predicted that a sphingid moth with a 

 tongue of the same length would be found ; such moths 

 have since been described from Brazil (Miiller, 1873) and 

 East Africa (Wallace, 1907). 



