AMEBIC AX CINQUE-FOILS. 191 



form, however, occurs nowhere in the United States except here on the 

 topmost summits of the White Mountains, and even there it lingers on 

 in scanty numbers, rapidly diminished by the growing warmth and the 

 incursions of botanists. I took but a tiny spray for my own specimen, 

 from a spot not far from Tuckerraan's Ravine, and left the remain- 

 der of the plant I found there still growing. It would be a pity if 

 these last survivors of the Glacial epoch, pushed up onto these chilly 

 heights by the secular summer of our own day, should be exterminated 

 by the hands of those who above all others are bound by natural piety 

 to preserve and protect them. 



All over Canada and the Northern States there grows a third and 

 very common potentilla, the cinque-foil or "five-finger" of popular 

 botany (P. Canadensis), a pretty, prostrate, creeping weed, with golden- 

 yellow flowers springing close to the ground, and five leaflets instead 

 of three to each leaf. Ever since the days of Linnaeus this plant has 

 been considered distinct from the common European cinque-foil (P. 

 reptans), and the differences are certainly sufiicient to justify their di- 

 vision as separate species, as systematic botany goes nowadays. Never- 

 theless, it is quite clear that we have here merely to deal with the 

 American descendants of the same old circum polar plant. No Euro- 

 pean naturalist who saw the Canadian cinque-foil for the first time 

 would ever take it for a distinct type ; if he found it growing in an 

 P^nglish meadow, he would certainly pass it by unnoticed as the famil- 

 iar cinque-foil of our eastern hemisphere. The differences can only be 

 observed when you look closely into the plant, and they are all of easy 

 adaptive character. In fact, we have here just the same tendency as 

 that which we noticed in the mountain species, only carried, perhaps, 

 one step farther. In that instance, the differences were only sufficient 

 for sytematic botanists to rank the plant as a mere variety ; in this case 

 they are sufiicient to give it the dignity of a distinct species. But at 

 bottom nobody knows what is a variety and what a species, and it is a 

 mere matter of individual judgment whether a particular form should 

 be regarded as one or the other. It varies " according to the taste and 

 fancy of the speller." Oakes considered the White Mountain poten- 

 tilla a distinct American species, different from the Alpine kind in Eu- 

 rope, and christened it, accordingly, P. Kohhinsiana, after the first per- 

 son who discovered it on these chilly hill-tops. Asa Gray regards it 

 rather as a mere variety, though he hesitates as to whether it comes 

 nearer to the P. frigida of the Alps, or to the dwarf form known as 

 P. minima (itself a very ill-marked species). It is always so when 

 you come to compare the plants or animals over a large area. However 

 distinct they may seem in particular localities, they shade off into one 

 another by such imperceptible degrees at distant points that the task 

 of drawing hard-and-fast lines, so lightly undertaken by the system- 

 atic biologist, becomes at last absolutely impossible. 



This very Canadian cinque-foil, for example, runs into two extreme 



