ORDEK 138.— THE ORCHIDS. '^^7 



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

 merous purplish-white flowers, in July. 



2. SAGITTA'RIA. Arrow-head. 



Flowers monoecious, rarelj dioecious, 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-flowcred. 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. Jul]/. 



Order CXXXYIII. ORCHID ACEJE. The Orchids. 



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

 flowers very irregular, but i\\Q> lyeriantli consisting always of 6 parts, viz., of 3 

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

 Zij? 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, furnished 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. . . .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 



3 Corolla prodnced into a spur behind, . . .b 



3 Corolla destitute of a spur 4 



4 Flowers small, many, in a loose raceme, beardless 6 



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. Ladifs-slipper. CvrRiPE'DiUM. 1 



a Root a corm. Lip 3-lobed, 2-spurred. Anther 1. Calypso. Calyp'so. 



