590 wherry: reactions of soils 



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The majority of the native orchids grow either in bog-peat 

 or in upland peat, both of which are usually acid in reaction. 

 Several species of the genera Cypripedium, Habenaria,^ Spi- 

 rant hes, etc., are, however, known to grow in limestone regions, 

 where the soil may possess a distinctly alkaline (basic) ^ reaction. 

 It seemed desirable to confirm these inferences as to the reac- 

 tions of the soils in all cases, for, as the following examples will 

 show, incorrect deductions may readily be drawn from superficial 

 examinations. 



In some limestone vallej^s in northern Pennsylvania and New 

 Jersey choked by glacial drift, swamps and bogs have developed 

 in which the standing water and underlying soil are alkaline, 

 owing to the presence of calcium bicarbonate in solution. The 

 orchids growing there, which include several C^pripediums, 

 Spiranthes lucida, Arethusa hulbosa, etc., might all be presumed 

 to be calciphilous and to require an alkaline soil. Actual tests 

 have shown, however, that while the tall Cypripediums do 

 indeed grow in the calcareous water, C. acaule and the other 

 two plants no'feed grow upon hummocks of sphagnum or other 

 mosses, where the soil proves to be decidedly acid in reaction. 



In other instances Cypripedium acaule, usually an acid soil 

 species, has been found in dry woods in limestone valleys, and 

 might have been classed as tolerant of alkaline conditions. 

 But in every case chemical tests have shown normal acidity, 

 and its roots have proved to be imbedded in sandstone drift so 

 thick as to exclude any possible effect of the underlying rock. 



1 The nomenclature of Gray's Manual, 7th edition, 19G8, is used here; for the 

 benefit of those who prefer other names, important synonyms are added in the 

 table containing the summary of results. In a study like the present it would 

 appear to make no difference what code of nomenclature is followed, so long as 

 the plants are correctly identified, and in this direction the utmost care has been 

 taken. 



- The term alkaline is here used in the physical-chemical sense, and has noth- 

 ing to do with the so-called "alkali" soils, in which there may be a neutral salt 

 of an alkali metal, so that the reaction is not necessary alkaline at all. Accord- 

 ing to the usage adopted, alkaline is essentially synonymous with basic, and 

 refers to the presence of free hydroxyl ions, and ability to neutralize acids, irre- 

 spective of the actual base present. 



