PHANEROGAMIA, 247 
of the same species, the pollen-masses are thrust against the 
sticky stigma (s¢) 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, pl; h, its sticky disc, below which isthe stigma. B, an open flower; 
J, its twisted ovary; 1, lip; st, stigraa; 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 slipper (lip), it does so 
