wherry: reactions of soils 597 



In conclusion, a brief discussion of some of the relations 

 brought out by the above table may be added. The separation 

 of Cypripedium acaule from the other species, and its assignment 

 to a separate genus, Fissipes, first proposed on purely botanical 

 grounds, may perhaps be regarded as having a chemical basis, 

 in that its soil reaction is markedly different from that of the 

 others. A similar case, although hardly sufficiently marked to 

 deserve taxonomic recognition, is that the Habenarias with a 

 simple fringed lip grow in distinctly more acid soils than do 

 those with a three-parted lip. 



In some instances the reaction of the soil appears to be more 

 important than its moisture content in determining where a 

 given species will grow; for a single species may be found in 

 habitats varying widely in wetness. Thus Cypripedium acaule 

 grows in wet sphagnum in various swamps, and in dry sandy 

 woods on the Coastal Plain; Spiranthes cernua in running water 

 in brooks, and in dry pine needles on some District of Columbia 

 and Pennsylvania hills; Liparis loeselii in oozy muck in the 

 swamps of northern New Jersey and Pennsylvania, and in 

 barren soapstone gravel on a steep slope along the Potomac 

 near Washington. Yet in every case the acidity of the soils 

 supporting each of these species varies within comparatively 

 narrow limits. This undoubtedly signifies that the fungus 

 living symbiotically on the roots of each species is less tolerant 

 of changes in acidity than in moisture. 



Finally, it may be worth while to consider the bearing of the 

 above data on the cultivation of the native orchids. It seems 

 obvious that the growth of the tall Cypripediums would be 

 favored by the addition of a little powdered limestone to the 

 soil; and the wTiter has been able to grow the northern C. 

 hirsutum successfully in the District of Columbia in this way. 

 On the other hand most species require the soil to be made dis- 

 tinctly or even strongly acid. This may be accomplished by 

 adding partly decomposed peat, by mixing in pure quartz sand, 

 and even by watering with highly dilute phosphoric acid or 

 acid phosphate solutions. It seems probable that if more 



