12S Rhodora [June 



thes." 1 He finds that typical Spiranthet cernua grows in association 

 with Calopogon and Arethusa, in "sour" soils, and in dry fields among 

 ericaceous plants. The soils in such habitats normally range in re- 

 action from specific acidity 300 down to 30 hut only exceptionally 

 go lower than that. This species is therefore evidently a high-acid 

 soil plant. It may be noted, further, that its occurrence both in bogs 

 and in dry fields shows that it, like other reaction-sensitive plants, 

 is relatively indifferent to the water content of a soil. 



Spiranthes cernua variety ochroleuca he states to grow, on the other 

 hand, in "woodlands and rich upland pastures," which are likely to 

 show a specific acidity of 10 or less. It appears, therefore, that this 

 variety is a low-acid soil plant. The w r riter has found it in bogs as 

 well as in w r oods, so that it also is indifferent to wetness or dryness. 

 The reaction relations of the two plants may be brought out by a 

 tabulation according to the plan previously used; the reaction ranges 

 of both of them are then seen to be of the order of magnitude common- 

 ly met with in individual varieties of orchids. 



Specific acidity 300 100 30 10 3 1 



Spiranthes cernua, typical x x x ? - - 



var. ochroleuca - - ? x x x 



Spiratiihes odorata has been found to favor subacid soils, being 

 thus intermediate in reaction between the above two. It is difficult 

 to agree, however, with Small, Britton & Brown, and Ames, that this 

 plant is conspecific with *S'. cernua; for where the two grow near to- 

 gether, as in the vicinity of Washington, D. C, they are distinct in 

 many respects, and have, moreover, been found to retain their dis- 

 tinctness when grown in cultivation side by side in the same subacid 

 soil. Some of their more striking differences are brought out by the 

 tabulation on the next page; Schlechter notes still others. 



The writer will be glad to send fresh specimens of both plants to 

 anyone who wishes to confirm these features, during the coming 

 September. 



It would be hard to imagine two members of a single genus being 

 more divergent; and search for intermediate forms in places where 

 the two grow in abundance within a few hundred meters of each other 

 has been unsuccessful. What might have been taken for an inter- 

 mediate has been collected in a cat-tail marsh at Cape May, New 



1 Rhodora, xxiii, 73, 1021. 



