Oedbe 138.— the orchids. 285 



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

 merous purplish-white flowers, in .July. • 



2. SAGITTA'EIA. Arrow-head. 



Mowers monoecious, rarely dioeoious, the S with about 24 stamens, 

 the 9 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- 

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

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



Order CXXXVIII. ORCHID ACEJE. The Orchids. 



Merls perennial, with thick, fleshy roots; entire, parallel-veined leaves; 

 flowers YQTj irregular, hut the perianth consisting always of .6 parts, viz., of 3 

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

 Up 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 

 sti/le 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 ^reen, furnished with one or more leaves 2 



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



* Stems brownish, furnished with sheaths and ilo leaves, or a late one. . . .o 



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



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



8 Corolla produced into a spur behind b 



8 Corolla destitute of a spur 4 



4 FloVers small, many, in a loose raceme, beardless o 



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

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



a Eoot fibrous. Lip obtuse, spurless. Anthers 2. Ladfe-sUpper. Ctpkipe'ditim. 1 



a Koot a corm. Lip 8-lobed, 2-spurred. Anther 1 . Galypao. Calyp'so. 



