330 
persion of seeds will be prevented. The farmer, 
who suffers weeds to remain till their ripe seeds 
are shed, and scattered by the winds, is not only 
hostile to his own interests, but is likewise an 
enemy to the public : a few thistles neglected soon 
will stock a farm ; and by the light down which is 
attached to their seeds, they may be distributed 
over a whole country. Nature has provided such 
ample resources for the continuance of even the 
meanest vegetable tribes, that it is very difficult to 
ensure the destruction of such as are hostile to the 
agriculturist, even with every precaution. Seeds 
excluded from the air, will remain for years inactive 
in the soil*, and yet germinate under favourable 
circumstances ; and the different plants, the seeds 
of which, like those of* the thistle and dandelion, 
are furnished with beards or wings, may be brought 
from an immense distance. The fleabane of Canada 
has only lately been found in Europe ; and Linnaeus 
supposes, that it has been transported from America, 
by the very light downy plumes with which the 
seed is provided. 
* The appearance of seeds in places where their parent plants 
are not found may be easily accounted for from this circum- 
stance, and other circumstances. Many seeds are carried from 
island to island by currents in the sea, and are defended by their 
hard coats from the immediate action of the water. West In- 
dian seeds (of this description) are often found on our coasts, 
and readily germinate; their long voyage having been barely suf- 
ficient to afford the cotyledon its due proportion of moisture. 
Other seeds are carried indigested in the stomach of birds, and 
supplied with food at the moment of their deposition. The 
light seeds of the mosses and lichens probably float in every 
part of the atmosphere, and abound on the surface of the sea. 
