266 GEOGRAPHY OF PLANTS. 



shew, which Brown found also in New Holland. Even the 

 Grasses and Cyperoidje share in this general distribution. A 

 great many native members of these families, as the Carex 

 raspiiosa, Scirpus liicustris^ Glyceriafluitans, Ariindo phrag^ 

 mites, Panicum Cms Gallic and so forth, grow also in New 

 Holland. Humboldt has confirmed these observations, in re- 

 spect to the growth of European Mosses, Grasses, and Cy- 

 peroida?, in South America. 



Higher and more perfect plants, on the contrary, are less 

 generally distributed by nature, although, by cultivation, they 

 also can be forced to vegetate in the most distant countries, 

 provided favourable circumstances occur. Of these circum- 

 stances, a considerable number must always co-operate for 

 the perfect evolution of plants of the higher orders. Yet 

 there are some exceptions to this rule. Verbena ojfficinaU-s, 

 Prunella vulgaris, Sonchus oleraceus, Hydrocotyle vulgaris, 

 Potentilla anserina, and some other common European plants, 

 grow also, according to Brown, in New Holland. Almost 

 the seventh part of the phanerogamous plants that vegetate 

 in North America are found in Europe ; yet we cannot deny 

 that many of them have been transplanted hither, (401.) On 

 Mascaren's Island, Bory St. Vincent found Cladium Germa- 

 nicum, Schrad., Cyperus Jusctis, Potamogeton natans, Hy- 

 drocotyle vulgaris, and some other European plants. 



393. 



The same distance from the equator, or the same degree 

 of latitude, produces rather a resemblance in the forms, — an 

 agreement in the families and genera, — than the same species, 

 chiefly because, besides this geographical latitude, the height 

 4ibove the surface of tlie sea, the temperature during the 

 growing season, the soil and constitution of the mountains, 

 even the degree of longitude, and several other circumstances, 

 have an influence on vegetation. 



There are a great many perfect plants which exclusively 

 belong to the tropics, which never pass beyond them, and 

 which are found equally in Asia and Africa, in America 

 and the South Sea Islands, and even in New Holland. Al- 



