GENERAL AND ENDEMIC DISTRIBUTION OF PLANTS. 569 



1145. Some plants are very much restricted in their distribution 

 over the globe ; a few are confined to single localities, while others 

 have a limited longitudinal range. The species of the genus Erica, 

 Heath, which extend from northern regions to the Cape of Good Hope, 

 are scattered over a surface very narrow compared to its length ; in 

 other words, while their latitudinal range is great, their longitudinal 

 range is very much restricted. Calceolarias occur chiefly on the wes- 

 tern side of the Cordilleras of Chili. Lobelia Dortmanna is found princi- 

 pally in the western countries of Europe. Camellias are also limited 

 in longitudinal direction, so also Phalangium bicolor, and Raymondia 

 pyrenaica. Arbutus Unedo, Erica mediterranea, and Menziesia poli- 

 folia, whose chief seat is in the Pyrenees and the mountains of 

 Asturias, migrate in a north-westerly direction, and appear in Ireland. 

 It is said that Azaleas, Rhododendrons, Magnolias, Vacciniums, Actaeas, 

 and Oaks, which form prevailing genera on the east of the Rocky 

 Mountains, scarcely appear on the western side. Epacridacese are 

 confined to New Holland; Cinnamon, Cloves, and Nutmeg, are the 

 produce of the Indian Archipelago ; Gentians and Saxifrages, form a 

 characteristic feature of the European Alps ; Bejarias and Cinchonas 

 of the Peruvian Cordilleras ; Schizanthuses of Chili ; Polemoniacese of 

 California and Oregon; yeUow and brown Papilionaceae of Australasia; 

 Disa grandiflora is a rare orchid peculiar to Table Mountain at the 

 Cape of Good Hope ; and Pringlea antiscorbutica is a cruciferous plant 

 peculiar to Kerguelens-land. It is said that Origanum Toumefortii 

 is found only on a small island in the Grecian Archipelago. The 

 vegetation of islands removed from continents presents often peculiar 

 features, the ocean acting as a barrier to the dissemination of plants. 

 The island of St. Helena was originally inhabited by a most peculiar 

 vegetation, although its productions now are completely changed by 

 the destruction occasioned by cattle, and by the introduction of Euro- 

 pean and other plants, especially fruit trees. Such may also be said 

 of the plants found in the Sandwich Islands, the Society Islands, and 

 the Canaries. The island of Madeira has 672 Phanerogamous plants, 

 of which 85 are peculiar to it. 



3 CONJECTURES AS TO THE MODE IN WHICH THE EARTH WAS ORIGINALLY 



CLOTHED WITH PLANTS. 



1146. It is an interesting question to determine the mode in which 

 the various species and tribes of plants were originally scattered over 

 the globe. Various hypotheses have been advanced on the subject. 

 Linnaeus entertained the opinion, that there was at first only one primi- 

 tive centre of vegetation, from which plants were distributed over the 

 globe. Some, avoiding all discussions and difficulties, suppose that 

 plants were produced at first in the localities where they are now seen 

 vegetating. Others think that each species of plant originated in, and 

 was diffused from, a single primitive centre, and that there were numer- 



