290 THE STORY OF PLANT LIFE 



fluent stigmas). The stamens in diandrous types 

 are of the inner whorl, and the middle fertile stamen 

 in the monandrous type is a large staminode. The 

 pollen does not occur in pollen-masses and is sticky. 

 The ovary is inferior, one-celled, long and twisted, 

 three-angled, with three parietal placentae as a rule. 

 The ovules are numerous, anatropous. The stigma 

 has a sticky face, formed by the union of three stigmas, 

 which are opposite the lip and below the rostellum in 

 monandrous types. The capsule is three-valved, with 

 many small seeds. The embryo is fleshy. 



Pollination in this group is of the greatest interest. 

 Many variations occur, but in general the method is 

 as follows. For details as to the mode adapted in 

 the different types, the reader is referred to the works 

 of Darwin. 



Honey is concealed in the spur. Many insects 

 drill a hole in the latter, which contains sweet sap. 

 An insect alights on the lip, and the pollinia, which 

 are sticky, are removed thereby attached to its head. 

 At the same time the insect displaces the ros- 

 tellum so that a sticky mass adheres to the insect. 

 The pollinia, when the insect enters another flower, 

 are brought into contact with the stigma, in some 

 cases being at first erect on its head, then becoming 

 more or less horizontal. 



The capsules open when ripe, and the seeds are 

 scattered by the wind. 



In their floral structure the Orchids are related to 

 the Iridaceae. 



