ORCHIDACE^ 



with Medeola virginiana, a species which at certain stages of 

 growth it resembles so closely, that references to the fact are 

 very numerous. This association is observed not only in the New 

 England States, but as far south as Virginia, and has been re- 

 ported by Prof. Earle Jerome Grimes from Williamsburg, Vir- 

 ginia, where Isotria verticillata prefers soils that are medium acid 

 to methyl red. 



If the flower of /. verticillata is compared in detail with a 

 flower of Pogonia ophioglossoides, it will be found that they dif- 

 fer markedly in the segments of the perianth. In the former the 

 front of the clinandrium is smooth, in the latter it is conspicu- 

 ously toothed. The differences that may be noticed in the lobing 

 of the lip, in the nature and structure of the keel and in minor 

 structures are specific rather than generic, therefore the weight- 

 iest character aside from pollen structure, on which to rely for 

 generic distinction from Pogonia, is the verticillate leaves and 

 the behavior of these in vernation. 



Westward from New England to Wisconsin and Indiana, southward to 

 Florida. Very much localized where found. 



Isotria affinis (Aust.) Rydb. in Britton's Man. (1901) 297. 

 Pogonia 2.ffims Aust. ex Gray Man. ed. 5 (1867) 507. Odonectis 

 affinis Schltr. in Engl. Bot. Jahrb. 45 (1911) 386. 



Isotria affinis, ever since its discovery by C. F. Austin near 

 Closter, New Jersey, has remained a rare species and is very spar- 

 ingly represented in herbaria. When met with, the plants are 

 reported as being in very much restricted areas where diligent 

 search is rewarded by the discovery of very few specimens. In 

 June 1920, the range of the species was extended southward to 

 Virginia by Prof. Earle Jerome Grimes, who discovered a colony 

 one and one-half miles southwest of Williamsburg. Prof. Grimes 



describes the locality where his specimens were observed as a flat, 



[18] 



