394 PHYSICAL GEOGRAPHY. 



and others, with arctic rushes, sedges, and lichens, which flourish on the 

 very summits. 



Introduced Plants. 



As shown from field-notes, there are more than one thousand species of 

 plants found in New Hampshire. Of these about one hundred are 

 "introduced," having been imported, either intentionally or otherwise, 

 through the agency of man. Some of them are indigenous in other 

 parts of our own country, but the greater part come from Europe. Many 

 of them have increased until they are found in all cultivated soils, while 

 others establish themselves only locally. In the former class are most 

 of the "weeds of cultivation," and nearly all the grasses mown for hay. 

 Most of these plants, although so well established under the present con- 

 ditions, would probably altogether disappear were the country allowed to 

 return again to its natural state. 



Unlike our indigenous species, these plants cannot be referred to any 

 particular portion of the state, because, having been planted accidentally, 

 they may be found regardless of altitude, &c., often in places where they 

 would least be expected. An instance is seen in the garden wormwood 

 (Artemisia Absinthium), rarely seen outside of gardens in most places, 

 but found well naturalized in Pittsburg, our most northern town, seem- 

 ing to find in the soil derived from the slaty rocks of that region the 

 conditions exactly suited to its growth. Instances of the wide range 

 which some of our introduced species have attained, may be seen in the 

 common hemp nettle (Galeopsis Tetrahit) and the herds-grass (Phleum 

 pratense). The former is common everywhere in the Merrimack valley, 

 passing into the valley of the Connecticut through Franconia notch, and 

 reaching northward to the clearings around Connecticut lake. The 

 latter, cultivated for hay throughout the state, may be seen in the lum- 

 ber roads throughout Coos county, and may even be traced up the car- 

 riage-road on Mt. Washington, far above the limit of trees. 



The white willow of Europe (Salix alba), which was at some time 

 introduced for a shade tree, has extended itself along the rivers, evi- 

 dently often without the aid of man, until now it may be seen as far 

 north as Stewartstown in the upper Connecticut valley. The Canadian 

 plum is much cultivated in Coos county, and may often be seen in places 



