ORDEK 138. THE ORCHIDS. 307 



veined, entire, on long petioles. Scape l-2f. high, branching in whorls, bearing nr 

 merous purplish-white flowers, in July. 



2. SAGITTA'RIA. Arrow-head. 



Flowers monoecious, rarely dioacious, the $ with about 24 stamen^ 

 the $ with numerous ovaries crowded in a head, and becoming in fruit as 

 many compressed, margined achenia. U Stemless plants, leaves radical, 

 generally arrow-shaped. Flowers in whorls of 3's, the sterile ones above 

 the fertile. 



S. variab'ilis. A curious plant, conspicuous with its large white flowers among the 

 rushes and sedges of sluggish waters. The petals are wholly white, and the 

 scape simple, with the stalks 1-flowered. The leaves are generally arrow- 

 ehaped (as seen in the figure), but exceedingly variable, sometimes lanceolate, 

 and sometimes even consisting of a petiole only. About If. high. July. 



ORDER CXXXYIII. ORCHID ACE^E. The Orchids, 



Herbs perennial, with thick, fleshy roots; entire, parallel-ve.ined leaves; 

 flowers very irregular, but ihe perianth consisting always of 6 parts, viz., of 3 

 sepah and 3 petals, all usually colored, the lower petal called the 

 lip differing in form from the others, and frequently spurred at base ; 

 stamens 3, but only 1 or rarely 2 of them perfect, united with the 

 style and forming what is called the column; Anthers 2, 4 or 8-celled; 

 pollen powdery, or waxy, or granulated ; ovary 1 -celled, many -seeded. 



Analysis of the Genera. 



* Stems green, famished with one or more leaves. ...2 



* Stems green, furnished with sheaths instead of leaves.... d 



* Stems brownish, furnished with sheaths and no leaves, or a late one....c 



2 Corolla lip very large, inflated and sack-like. ...a 



2 Corolla lip of various forms, but neither very large nor sack-like ... .8 



3 Corolla produced into a spur behind . . . .b 



8 Corolla destitute of a spur.. . .4 



4 Flowers small, many, in a loose raceme, beardless....* 



4 Flowers small, many, in a close, twisted spike, beardless.... f 



4 Flowers showy, purple or yellow, few or 1 only g 



a Root fibrous. Lip obtuse, spurless. Anthers 2. Lady* s-slipper. CYPRIPK'EIUM. 1 



a Root a corm. Lip 8-lobed, 2-spurred. Anther 1. Calypso. CATTP'SO. 



