598 THE POPULAR SCIENCE MONTHLY. 



dryas, and not unlike it in general effect. Anybody who cultivates 

 rock-gardening, indeed, must be thoroughly familiar with this curious 

 mat-like habit of the northern mountain flora ; for many of the saxi- 

 frages, alyssums, arenaries, and stone-crops which form his favorite 

 masses of bloom are members of this truly Alpine and sub-Arctic vege- 

 tation. Often their very names betray their origin : lovers of rock- 

 gardens will know what I mean when I mention such cases as JEJrinns 

 Alpinus, Lychnis Lapponica, Seclum Kamschaticum, Alyssum mon- 

 tanum, Silene alpestris, Dianthus petrceus, Saxifrage nivalis, and 

 Arenaria montana. 



Nor is it only herbaceous species that undergo this curious dwarf- 

 ing and acquire this strange matted tuftiness, in order to meet the needs 

 of high Arctic and Alpine situations. Trees and bushes have similarly 

 to accommodate themselves to the exceptional conditions of the snow- 

 line and the region just below it. Every tourist who goes up Mount 

 "Washington must have noticed how, near the limit of arboreal vegeta- 

 tion, the pines and spruces grow shorter and more stunted by slow de- 

 grees, till at last they disappear altogether from the scene. But even 

 after they are gone, so far as the naked eye is concerned, they persist 

 in part for the eye of the botanist. Three dwarf willows, for example, 

 occupy the summits of the White Mountains, beyond the so-called 

 limit of trees. All of them are prostrate, matted, and Alpine in type ; 

 none of them rises above the general level of the herbaceous vegeta- 

 tion in whose midst they are found. The first, known as Cutter's wil- 

 low, may also be gathered among the other higher mountains of the 

 exti'eme Northern States, such as the Adirondacks and the Maine 

 ranges. The second, the silvery-pointed willow, a very pretty plant 

 of glossy, satin-like sheen when young, is confined to the moist Alpine 

 ravines of the White Mountains themselves. The third and most 

 dwarfish species of all, the herbaceous willow, has lost all resemblance 

 of its descent from what was once a forest tree, and has degenerated 

 into a rare ordinary herb, seldom rising above an inch or two from 

 the ground, but still producing from its terminal buds the tiny cat- 

 kins which keep up the memory of its former high estate. This last de- 

 graded scion of the willow stock, which creeps and roots underground 

 for considerable distances, is common to both sides of the Atlantic, 

 being found also in the Alps and Pyrenees, as well as in Arctic and 

 sub-Arctic Europe : but the White Mountains are its only known sta- 

 tion in the United States. 



It is interesting to note that just the same dwarfing of the trees 

 and shrubs took place everywhere during the fiercest rigor of the 

 Glacial Epoch. In the little bed of glacial clay, containing plant re- 

 mains of the Great Ice Age, on the coast of Norfolk in England, we 

 still find the leaves of a tiny, shrubby birch (Betula nana), which 

 grows even now in the Highlands of Scotland and in Scandinavia, 

 attaining there at times to tree-like size, but which dwindles near the 



