NATURAL HISTORY OF PLANTS. 27 



flat, have all the plants of the neighbouring continent ; but if they 

 contain high mountains, they are not unfurnished with the plants 

 that grow on those. 



Tims, though according to these observations, no great changes 

 had happened to the plants at present existing, every hypothesis 

 that should maintain the remains of the vegetable kingdom, to be 

 still existing plauts, would be destitute of probability. 



May not the sea have formerly been more extended over the 

 globe than it is at present ? Perhaps the earth consisted at first of 

 a vast watery plain, broken only by chains of high mountains, and 

 the depth of the sea might be smaller. On these mountains existed 

 the vegetation of the present land. . The sea might chuse itself a 

 deeper bed, the mountain would decrease, and the firm land by 

 degrees appear, which would gradually be sown with the plants of 

 the mountains and the vallies. Here and there the sea might leave 

 large lakes of salt water, which would gradually dry up, and leave 

 behind the hard rock salt. This bed of salt would, according to 

 circumstances, by the waves of the sea or by high winds, be covered 

 with earth, or with mud convertible into hard stone. The shore of 

 the sea nourishes, as is well known, its own peculiar plants, which 

 flourish in a soil abounding with salt, but perish where there is 

 none. In the neighbourhood of these beds of salt, the shore plants 

 would find sufficient nourishment and increase. Subterraneous 

 springs of fresh water would flow over these salt beds, and being 

 impregnated with the fossil would appear as salt springs. The shore 

 plants would here find plenty of nourishment, and would propagate 

 rapidly. This appears to be the origin of salt springs, and perhaps 

 accounts for the appearance of the shore plants in their neighbour- 

 hood. We accordingly find near 'salt springs in the interior of 

 Continents, the following plants of the sea shore, which are no 

 where else to be met with, viz. Salicoruia herbacea, Poa disfans, 

 Plantago marittma, subulata, Glaux mwritima, Saniolus Vale- 

 randi, Aster Tripolium acris, and many others. 



When in this way, perhaps after a long succession of years, as we 

 suppose, the land was gradually formed, hurricanes, earthquakes, 

 and volcanoes, mighty again destroy large traits, and change the 

 form of the land, by which means a number of plauts might be 

 destroyed that afterwards might never appear again We find most 

 plants growing in their native places plentifully, but there are some, 



