ORCHIDACEM. 



241 



flower: 1st, the flower is irregular (the parts of a set are differ- 

 ent in size and shape); 2d, adnation of all parts with the pistil; 

 3d, reduction and suppression 

 of the stamens; 4th, the ovary is 

 twisted half way around so that 

 the posterior side of the flower 

 becomes anterior. Floral dia- 

 grams in fig. 207 show the posi- 

 tion of the stamens in two dis- 

 tinct types. The number of 

 orchid species is very large, and 

 the majority are found in tropical countries. 



392. Pollination of orchids. — Some of the most marvellous 

 adaptations for cross-pollination by insects are found in the 



Fig. 207. 

 Diagrams of orchid flowers. A , the usual 

 type ; B, of cypripedium. (Vines.) 



Fig. 209. 

 Section of flower of cypripedium. j/, 

 stigma : a , at the left stamen. The insect 

 enters the labellum at the centre, passes 

 under and against the stigma, and out 

 through the opening l>, where it rubs 

 against the pollen. In passing through 

 another flower this pollen is rubbed off 

 on the stigma. 



orchids, or members of the orchis family. 

 The larger number of the members of 

 this family grow in the tropics. Many of 

 these in the forests are supported on lofty trees where they are 

 brought near the sunlight, and such are called "epiphytes." 



Fig. 208. 

 Cypripedium. 



