CLASSIFICATION OF THE MONOCOTYLEDONS. 165 



ovary) of the inner set. This petal, known as the "lip" or 

 "labellum," is usually larger than the others, and different 

 in color, as well as being frequently of peculiar shape. In 

 many of them it is also prolonged backward in a hollow spur 

 (see Tig. 89, B) . In all of the orchids except the lady's-slippers 

 (Cypripedium) (Fig. 90, B), only one perfect stamen is devel- 

 oped, and this is united with the three styles to form a special 



D 



FIG. 90. Forms of Orchidese. 



x 1. B, yellow 



A, putty-root (Aplectrum) , 



lady's-slipper (Cypripediurri) , x %. C, the column of the same, x l. an. 

 one of the two perfect stamens, st. sterile, petal-like stamen, gy. stigma. 

 D, Arethusa, x %. E, section of the column, x l. an. stamen, gy. stigma. 

 F, the same, seen from in front. G, Habenaria, x 1. H, Calopogon, x 1. In 

 the last the ovary is not twisted, so that the lip (L) lies on the upper side of 

 the flower. 



structure known as the "column" or " gynostemium " (Fig. 

 89, B, C). The pollen spores are usually aggregated into two 

 or four waxy masses (" pollinia," sing, pollinium), which usually 

 can only be removed by the agency of insects upon which all 

 but a very few orchids are absolutely dependent for the pollina- 

 tion of the flowers. 



