96 Dr, Dawson on tlie Flora 



lat. 55° to 65*^ in Arctic America, and according to Hooker it is 

 found in the Rocky Mountains, while it also occurs in the hills of 

 •Scotland, and very abundantly in some parts of Norway. In the 

 White Mountains aS'. thyrsoidea prevails toward the base, S. virga- 

 aurea toward the summit ; and at the top of Tucker man's ravine 

 I found the former of these golden-rods in blossom, within a few 

 hundred feet of the latter, each preserving its distinctive peculi- 

 arities. Much has lately been said of the appearance of specific 

 diversity that results from the breaking up of the continuity of 

 the geographical areas of plants by geological changes ; but here 

 we probably have the converse of this. The mountain species is 

 no doubt a part of the older arctic flora, the other belongs to the 

 more modern flora of the plains, and they have met on the sides 

 of the White Hills. 



Some hardy species climb from the plains to heights of 5000 

 feet or more, with scarcely even the usual change of being de- 

 pauperated, and then suddenly disappear. This is very note- 

 worthy in the case of two woodland plants, the dwarf cornel or 

 pigeon-berry {Cornus Canadensis), and the twin-flower (^Linnosa 

 borealis). The former of these is a plant most widely distributed 

 over northern America, and probably belongs to that newer flora 

 which overspread the continent after its re-elevation. In August 

 this plant in the woods around the base of Mount Washington is 

 loaded with its red berries. At an elevation of four to five thousand 

 feet it may be found in bloom ; above this a few plants appear 

 destitute of flowers, dwarfish in aspect, and nipped by cold, and 

 then the species disappears. No doubt the birds that feed on its 

 little drupes have carried it up the mountain, and have sown it a 

 little farther up than the limit of its probable reproductiveness. 

 The beautiful little Linncea is a still more widely distributed 

 plant; for it occurs on the hills of northern Europe, and is found 

 across the whole breadth of the American continent from Nova 

 Scotia to the Columbia River. It is almost beyond question a 

 member of the old arctic flora which colonised the islands of the 

 Post-pliocene sea, and has descended from them on all sides as 

 the land became elevated. This plant also climbs Mount Wash- 

 ington to a height of 5000 feet, and presents precisely the same 

 characters on the top as at the bottom, only losing a little in the 

 length of its stem. Specimens bearing blossoms and quite in the 

 same stage of growth, may be collected at the same time on the 

 highest shoulders of Mount Washington, and on the flats at Gor- 



