392 PHYSICAL GEOGRAPHY. 



and shield ferns, where also, clinging to moss-grown boulders, are the 

 handsome evergreen fronds of the common polypody. The dwarf and 

 ebony spleenworts and the frail bladder fern delight to find a lodgment 

 in the crevices or at the base of perpendicular ledges. 



Our state may be called the home of the Lycopodiums or club mosses, 

 popularly known as "trailing evergreen," all excepting two of those 

 belonging to the Northern states being present. They are found in deep 

 woods and on cold, bleak hillsides, and are most common on the high- 

 lands of Cheshire county and around the base of the White Mountains. 



The Alpine Flora. 



The wind-swept summits of our White Mountains are to the botanist 

 the most interesting locality east of the Mississippi, for there are found 

 the lingering remnants of a flora once common probably to all New Eng- 

 land, but which, since the close of the glacial epoch, has, with few excep- 

 tions, retreated to Arctic America. On the highest of these mountains, 

 only, are found the conditions favorable to the growth of these arctic 

 plants. Of these alpine areas, Mt. Washington and the adjacent peaks 

 are the largest, being a treeless region at least eight miles long by two 

 miles wide at its broadest part. These alpine plants are of great hardi- 

 hood, and sometimes bloom amid ice and snow, as a Greenland sandwort, 

 found in bloom on the summit of Mt. Washington by Mr. S. A. Nelson, 

 March n, 1871, well illustrates (p. 114). About fifty species are strictly 

 alpine, and never found elsewhere with us. These are accompanied by 

 about as many other species, which are also found at the base of the 

 mountains, and sometimes throughout the state. These may be called 

 sub-alpine, being found in the ravines and on the lower portions of the 

 treeless areas, but not upon the higher summits. 



The peculiar flora of these heights, almost wholly consisting of plants 

 never found at lower elevations south of arctic latitudes, but identical 

 with those found on Mt. Katahdin in Maine, and the Adirondacks in New 

 York, has led naturalists to inquire how it is possible to account for this 

 identity of species found at a few isolated stations in the midst of the 

 temperate zone, with those of regions more than a thousand miles north. 

 The conditions of climate which prevail over the intervening territory 

 render it impossible for these plants to maintain their existence, and 



