THE FORMS OF FLOBAL ORGANS. 109 



adhesions of the stamens to the corolla furnish the fulcra, 

 the cohesion of the petals into a tube aifording a greatly 

 increased power of resistance ; the weight of the insect on 

 the labellum or declinate stamens is, of course, vertically 

 downwards, and the line of the resultant, which the lip 

 in Lamium and the stamens whenever declinate have to 

 exert, passes through the point of meeting of the first 

 two, and so sustains the insect while visiting the flower. 

 Other and analogous instances will be described here- 

 after. 



Good illustrations of the occurrence of great thickenings 

 just where the strain will be most felt, Etay be seen in the 

 slipper-shaped flowers of Calceolaria (Fig. 32), Coryanthes, 

 and Cypripedium. Thus Calceolaria Pavonii 

 possesses a thick ridge along the upper 

 edges of the curved basal part, which 

 carries the inflated end upon which the 

 bee stands, and which it depresses to get 

 the honey. In this species it may be 

 noticed the anther-cells are separated (a), 

 so that they can oscillate as they do in Fig. 32.— calceolaria Pa- 

 Salvia. In Cypripedium the edge is folded "™" ^^^' ^"''"'• 

 inwards, thus strengthening the same part; while in Cory- 

 anthes the lower portion is enormously enlarged, thus acting 

 as a powerful spring which forces the anterior end of the 

 labellum to be in close contact with the column. 



The Origin of Ieeegulaeitt in the Andrcecidm. — As it 

 is with the perianth, so is it with the andrcecium : if the 

 petals are regular the stamens are usually regular also ; but 

 when irregularity occurs in the corolla the staminal whorl 

 follows suit, and the position and form of the stamens are 

 equally correlated to the efEectnal pollination of the flower. 

 Thus, as hypertrophy affects the anterior side of the 

 12 



