44 



McMurtrie's book appeared, the Geddes, N. Y. station, was the 

 only one then known in America, having been recorded by Pursh 

 just five years previously. 



CONCLUSIONS. 



I have described with considerable fullness the American local- 

 ities where Phyllitis Scolopendrium is known to have been found. 

 The striking and invariable characteristic of its environment ap- 

 pears to be an affinity for limestone rocks the Corniferous in cen- 

 tral New York ; the Guelph Dolomite and Clinton in Ontario ; the 

 Bangor (Mountain) limestone in Tennessee, representing consid- 

 erable range in choice of formations. The question naturally 

 arises : Why should the number of known localities be so small ? 



As a matter of fact, the Hart's-tongue is, as I have indicated, 

 far more common than has usually been thought ; and it will prob- 

 ably turn up continually in some of the less explored regions of 

 Canada, especially in the northwest. It appears to require for its 

 best growth a cool, well-shaded limestone ravine, talus, or sloping 

 woodland, with rich wood soil, for the most part sufficiently porous 

 to allow free drainage, but firm enough to retain considerable 

 moisture. Such conditions occur in hundreds of glens in the 

 United States and Canada. There is moreover, quite a wide vari- 

 ance, in the wet heavy clay of the South Pittsburg sink-hole, from 

 the rich porous soils and loose leaf moulds of the central New York 

 stations, or the scant soil, of the limestone crevices in some of the 

 Owen Sound stations. The South Pittsburg clayey habitat is, to be 

 sure, somewhat anomalous, but it appears that almost any soil 

 upon limestone will support the fern under the right temperature 

 conditions, perhaps the most important factor now operating for 

 or against the fern's survival and in determining its future distribu- 

 tion, is the presence of a constant low temperature. The James- 

 ville pit-lakes have a uniformly cool temperature from day to day. 

 The Chittenango gorge is deep and the fern is well shaded. Ferns 

 growing from fifty to seventy-five feet below the surface, as in 

 the irregular South Pittsburg chasm, cooled by a waterfall, can be 

 affected only in slight degree by extremes of temperature. The 

 Canadian stations are mostly near streams. It is true also that 

 extremes of cold do not seem to affect this fern deleteriously. It 

 remains evergreen through ordinarily severe winters, except when 

 unduly exposed by removal of protective forest growth. And so, 

 while the fact of an even low temperature does not adequately 



