DISTRIBUTION OF PLANTS. 1 3 



eumstances, representative, but not identical. 

 Thus, the Flora of the United States of North 

 America is totally different from that of Europe, 

 even in places where the annual temperature is 

 the same. Of 2,891 species of flowering plants 

 found in the United States, only 385 are com- 

 mon to them and the corresponding latitudes of 

 Europe. In St . Helena, of thirty flowering plants , 

 only one or two are native elsewhere. In the 

 Galapagos islands, out of 180 plants which have 

 been collected, 100 are found nowhere else ; 

 and of twenty-one species of composite plants, all 

 but one are peculiar to that group. Some few 

 species make the most remarkable leaps, being 

 common to countries at a great distance from 

 each other, while absent, or nearly so, from the 

 intervening ones. Thus, in the Falkland Islands, 

 more than thirty plants, natives of Britain, are 

 found wild. The common quaking-grass (Briza 

 media) has been found in the interior of the 

 country at the Cape of Good Hope ; and almost 

 all the lichens brought from the southern 

 hemisphere by sir James Eoss, amounting to 

 200 species, are found in the northern hemi- 

 sphere, and chiefly in Europe. Several of our 

 commonest plants, as the bull-rush, (Typhaan- 

 gustifolia,) the reed, (Arundo pliragmites,) the 

 marsh-mallow, (Althcea qfficinalis,) the bird's- 

 foot trefoil, (Lotus corniculatus,} the knot-grass, 

 (Polygonum aviculare,) with several others, are 

 found again in Australia. For this various 

 distribution of plants it is difficult to account. 

 A recent theory, which has been ably advocated 

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