FLORA OF THE DISTRICT OF COLUMBIA. 131 



3. Ibidium odoratum (Nutt.) House. Fragrant ladies'-tresses. 

 Swamps; Alexandria and Dyke. Sept. Along the coast, Va. to Tex. {Spiranthes 



odorata Lindl. ; Gyrostachys odorata Knntze.) 



The stolons spread out under water from the base of the plant for several inches and 

 end in a large green bud at the surface. 



4. Ibidium vernale (Engelm. & Gray) House. 



Dry meadows. July. Eastern U. S. {Spiranthes vernalis Engelm. & Gray.) 



5. Ibidium gracile (Bigel.) House. 



Open meadows in dry pine and oak woods. July-Aug. Eastern U. S. {Spiranthes 

 gracilis Beck; Gyrostachys gracilis Kuntze.) 



6. Ibidium beckii (Lindl.) House. 



Open meadows and dry woods. Aug.-Sept. Coastal Plain, Mass. to Tex. {Spiran- 

 thes beckii Lindl.; S. simplex A. Gray; Gyrostachys simplex Kuntze.) 



11. PERAMITJM Salisb. Rattlesnake plantain. 



1. Peramium pubescens (Willd.) MacM. 



Pine and oak woods. Aug. Eastern U. S. {Goodyera pubescens R. Br.; Epipactis 

 pubescens A. A. Eaton.) 



There is a specimen of Peramium ophioides (Fernald) Rydb. in the herbarium 

 labeled "N. W. Branch, Sept. 28," but the data are regarded as doubtful. 



12. OPHRYS L, TWAYBLADE. 



1. Oplirys australis (Lindl.) House. 

 Bladensburg Swamp. May. N. Y. to La. {Listera australis Lindl.) 



13. CORALLORRHIZA R. Br. Coral-root. 



Lip with a small lobe on each side at the base 1 . C. maculata. 



Lip not lobed at the base. 



Lip denticulate, long-clawed; plant flowering in May 2. C. wisteriana. 



Lip notched at the apex, short-clawed; plant flowering in August. 



3. C. odontorliiza. 



1. Corallorrhiza maculata Raf. 



Medium rich oak woods. Aug.-Sept. Throughout the U. S. {C. multiflora 

 Nutt.) 



2. Corallorrhiza wisteriana Conrad. 



Apparently confined to rich woods along the Potomac. May. Eastern U. S. 



3.- Corallorrhiza odontorhiza (Willd.) Nutt. 

 Medium rich woods, often under beech. Eastern U. S. 



14. MALAXIS Soland. Adder's-mouth. 



1. Malaxis unifolia Michx. 



Along runs in ravines of dry woods. July. Eastern U. S. {Microstylis ophioglos- 

 soides Nutt.; Achroanthes unifolia Raf.) 



15. LIPARIS L. Rich. Twayblade. 



Lip wedge-obovale, purjile 1. L. liliifolia. 



Lip oblong-ovate, yellowish green 2. L. loeselii. 



1. Liparis liliifolia (L.) L. Rich. 



Medium rich oak woods. June. Eastern U. S. {Leptorchis liliifolia Kuntze.) 



2. Liparis loeselii (L.) L. Rich. 



Rocky ravines and rich woods. June. Northern states, south to Md. {Leptorchis 

 loeselii MacM.) 



