BOTANY. 369 



cent vegetation, especially at great distances from the sea, is proved by sev- 

 eral facts. European Russia is a vast plain, resembling in geographical 

 structure the prairies of the West, and, like them, subject to long droughts, 

 which cannot fail to operate injuriously on the vigorous development of 

 trees. Accordingly, the Russian forests, though very extensive, furnish no 

 durable timber; and the Russian ships are remarkable for their great lia- 

 bility to decay. The dry-rot which invariably attacks them is ascribed to 

 the peculiar character of the waters of the Baltic and Black seas ; but, as it 

 does not seem to operate very injuriously on British vessels which enter the 

 same ports, we can only attribute the effects to the great difference in the 

 durability of the wood used by both nations for shipbuilding. On this con- 

 tinent, the mountainous districts and the lands near the sea coast produce 

 the most durable timber; while in the inland states and territories, and es- 

 pecially in the Mississippi Valley, arborescent vegetation displays less vigor, 

 and hollow trees become more numerous. 



It is not surprising that, where the gigantic forms of vegetation are ex- 

 posed to such enervating influences, they should be incapable of contending 

 successfully with the herbaceous plants for the possession of the soil, and 

 that the forest fails to maintain its ground in such localities. Accordingly, 

 trees are absent from prairies, except on the banks of rivers, where they are 

 favored with copious dews, or in barren soil, where their growth is slow, 

 and the supply of nutriment is not too copious for the energy of vegetative 

 power. As the steppes of Central Asia and the pampas of South America 

 exhibit the same peculiarity, we may reasonably suppose that natural causes 

 alone are sufficient to establish permanent boundaries between the domin- 

 ions of the trees and those of the herbaceous plants, and to prevent the for- 

 est from acquiring the exclusive possession of all lands. 



To cultivate trees successfully on prairies, and to prevent their degeneracy, 

 it would be necessary to introduce seed from regions more favorable to their 

 health ; for seeds, to a certain extent, receive and transmit the infirmities of 

 the plants which produce them. The oaks raised in England from German 

 acorns are found to be much inferior to those generally grown in the British 

 forests. In prairies, also, it will be necessary to plant the trees a considera- 

 ble distance apart, in order to permit the utmost expansion of their foliage, 

 and thus cause the elaboration of the sap and the formation of woody fibre 

 to take place in a more effective manner. The character of the wood of all 

 trees is always impaired by the removal of their leaves or branches ; and, 

 according to Loudon, pruning has been abandoned in the cultivation of the 

 British forests, as experience proved its deleterious influence on the durability 

 of the timber. 



But, notwithstanding this result, pruning serves to maintain the sap in a 

 condition suited to the nutriment of fruit ; and it becomes more necessary in 

 climates where rains are frequent, and the tendency to form woody fibre 

 very great. In dry climates it should be pursued, with more caution, and 

 many diseases to which fruit trees are subject proceed from over-pruning. 

 During the dry summer of 18-54, it was observed in Southern Ohio that the 

 unpruncd grape-vines were most productive. On a farm near Xew Rich- 

 mond, Ohio, were some grape-vines which were never pruned, and, after 

 being unproductive for many years, they bore grapes in abundance in the 

 summer of 18-34, while the rest of the vineyard, which was cultivated in the 

 usual way, afforded only a small crop. These facts show that a deficiency- 



