208 MISC. PUBLICATION 42 3, U. S. DEPT. OF AGRICULTURE 



This large family, mainly tropical, includes some of the handsomest 

 of all flowers. The species most extensively grown as ornamentals are 

 mainly tropical and epiphytic. The Arizona species are all terrestrial 

 (rooted in soil) and have relatively inconspicuous flowers, excepting the 

 ladyslipper {Cypripedium) and Calypso. All orchids are interesting, 

 however, because of the complicated structure of their flowers, which 

 are specialized for pollination by various insects. It is remarkable that 

 notwithstanding the enormous number of seeds produced, these plants 

 are usually rare and seldom abundant. Aside from the value of some 

 of the species in the florist trade, the family is of little importance 

 economically, except that extract of vanilla is manufactured from the 

 pods of certain climbing species of tropical America. 



Key to the genera 



1. Plants without green coloring matter, yellowish or purplish brown; inflorescence 



not spirally twisted; roots none; rootstock thick, corallike; leaves reduced to 



sheathing scales; flowers several or numerous, in a raceme (2). 



2. Lip entire, erose, or with a pair of short lobes near the base, with a small 



callus or fold on each side of the mid vein; perianth much less than 2 cm. 



long 7. CORALLORRHIZA. 



2. Lip 3-lobed toward the apex, with several longitudinal winglike crests; 



perianth about 2 cm. long 10. Hexalectris. 



1. Plants with green, well-developed leaves or, if not so, then the inflorescence 

 spirally twisted; roots present; rootstock, if any, not corallike (3). 



3. Fertile anthers 2; lip an inflated sac 2 to 5 cm. long 1. Cypripedium. 



3. Fertile anther 1; lip not more than 2 cm. long (4). 



4. Spur of the lip distinct, saccate to elongate-clavate 2. Habenaria. 



4. Spur of the lip none or obscure (5). 



5. Lip not saccate or strongly concave (6) . 



6. Flowering stem not from a bulb; leaves 2; lip longer than the sepals, 

 short-stalked, the blade broadest at the retuse or obcordate 

 apex 5. Listera. 



6. Flowering stem from a bulb; leaf solitary; lip shorter than the sepals, 



sessile, broadest near the base, entire or nearly so at apex. 



8. Malaxis. 

 5. Lip saccate or strongly concave, at least toward the base (7). 



7. Leaf solitary, this and the scape arising from a corm ; flower solitary, 



the lip conspicuously bearded, much larger than the other perianth 



segments 9. Calypso. 



7. Leaves several; corm none; flowers several or numerous; lip beardless, 

 not, or not much, larger than the other segments (8). 

 8. Plant acaulescent ; foliage leaves in a basal rosette ; flowers pubescent ; 



lip strongly concave, erect 6. Goodyera. 



8. Plant caulescent, the stems leafy; flowers glabrous; lip concave only 

 toward the base (9) . 

 9. Flowers greenish or purplish, in a loose raceme; sepals and 

 petals separate, spreading; column not beaked. 



3. Epipactis. 



9. Flowers ochroleucous, in a spirally twisted, spikelike raceme; 



sepals and petals united or connivent, forming a galea over 



the column; column slender-beaked 4. Spiranthes. 



1. CYPRIPEDIUM. Ladyslipper 



Flowering stems from a cluster of somewhat thickened roots, leafy; 

 herbage glandular-pubescent; leaves large, oval, sessile, strongly 

 nerved; flower usually solitary; lip large, yellow, saccate, the other 

 perianth segments long and narrow, greenish or brownish purple; 

 stamens 3, the upper one sterile and somewhat petaloid, covering the 

 summit of the style; stigma broad, slightly 3-lobed. 





