PllANEBOaAMIA. 



247 



of the same species, the pollen-masses are thrust against the 

 sticky stigma {st) and all or a part adheres to it. Thus, as 

 the insect passes from flower to flower, it unconsciously 

 pollinates them, always, however, carrying the pollen of 

 one flower to the stigma of some other. 



521. The Lady's Slippers are examples of Orchids with 



Fig. 138— An Orchid-flower (Orchis mascula). A, vertical section of a flower- 

 bud (magnified) before it has twisted upon its ovary, /; gs, the column, bearing a 

 pollen-mass. p2; h, its stickydisc, below which is the stigma. B, an open flower; 

 /, its twisted ovaiy; I, lip; st, stigma; a, anther; h, its sticky disc; sp, spur. 



two anthers; these are upon the sides of the curved column 

 which bears the stigma higher up. The lip is here shaped 

 like a slipper (whence the common name), into the opening 

 of which the column bends. The lip and the other parts 

 of the perianth are colored, often showing striking con- 

 trasts, and these doubtless serve to attract the notice of 

 insects. When an insect enters the slippe/* (Up), it does so 



