Sibbaldiopsis tridentata Found in the Catskills 



Raymond H. Torrey 



In a previous note regarding the scattered distribution of 

 Sibbaldiopsis {P otentilla) tridentata, on mountain tops from Maine 

 to North Carolina, and its absence, so far as I then knew, from any 

 of the Catskill summits, and the Great Smokies in Tennessee, 

 which were included in my personal observations, I speculated 

 whether theplantdidnotpreferexclusivelyopen, bleak situations. 



I have recently received two interesting communications on 

 this subject: one from Dr. Edgar T. Wherry, Chief of the 

 Bureau of Chemistry and Soils of the United States Depart- 

 ment of Agriculture, explaining the occurrences of Sibbaldiopsis 

 on the basis of its probable intolerance of shade, and the other, 

 from Mr. William Gavin Taylor, of Arlington, N. J., reporting 

 that he found the plant in the Catskills, on Overlook Mountain, 

 a summit which I had not examined. Mr. Taylor's location, on 

 an open ledge, at the brink of a cliff, overlooking the Hud- 

 son Valley, with a sweep of northern winds for a hundred miles, is 

 possibly the only stand of the plant in the Catskills. I am sure 

 it is not found on more than twenty other high summits on which 

 I have looked for it, in this region. 



Dr. Wherry wrote, regarding my inquiry as to the distribu- 

 tion of Sibbaldiopsis: "I have been trying to work out some 

 explanation of this based on the chemical character of its soils, 

 but without success. It seems to grow on gravelly soils irrespec- 

 tive of their derivation, although always acid in reaction. So my 

 conclusion would be that this plant is absent on some mountains 

 where one might expect it because it is so intolerant of shade and 

 competition. It evidently survived the glacial period on the peaks 

 of the Blue Ridge in Virginia and North Carolina — by the way, 

 these are largely of Archaean rocks — and then gradually mi- 

 grated northward when the ice retreated. Carrying of seeds by 

 the wind seems out of the question, so birds are the only likely 

 means of transportation. I suppose that once in a thousand 

 years a seed of it might stick to a bird's feet or feathers, and 

 when this bird alighted on another similar peak for food the 

 seed dropped off and started a colony there. Under such circum- 

 stances chance evidently plays a large role, and the absence of the 

 plant on a particular mountain might merely mean that this 'ac- 



19 



