172 
THE VEGETABLE WORLD. 
Wind, running water, blocks of ice drifting in the Polar seas, 
the action of animals and men—that is, by cultivation—ships, 
Fig. 269.—Starch Grains of the Potato. 
merchandise, and voyages; 
such are the causes, more or 
less powerful, which effect the 
conveyance of seeds from one 
place to another. If we con- 
sider how many seeds are 
light, hairy, and provided with 
a sort of wings in their downy 
tufts, we can understand that 
the wind may be the most 
general and ordinary means 
for disseminating vegetable 
germs over acountry. Rivers 
also carry away the seeds of 
plants to great distances. If 
their course runs from north 
to south, or the contrary way, the wandering seeds would 
\ 
Fig. 270.—Starch Grains of Maize, 
carried to a climate where they could 
not live; but if the river flows from 
east to west, or from west to east, the 
seeds thus transported would much 
extend the limits of the species. The 
currents of the sea, which skirt the 
coast, or extend from one country 
to a neighbouring one, carry 
22 seed, so to speak, from one storing- 
place to another. In the latter case 
the seeds remain but a short time 1 
the water, and are little altered in 
consequence; besides, the graduate 
temperature of the successive locali- 
ties which they reach is favourable 
to their acclimatisation and to ther 
further development. The opeT 
tion of blocks of ice in the transport 
of seeds is not without a certain importance. Navigators of the 
