Means of Dispersal. 2 
and Cornwall, and of the peculiar eastern-county plants 
belong to this group, the larger seeded species found 
associated with them on the Continent being absent. 
These plants seem therefore to possess in a pre-eminent 
degree the power of crossing seas like that which separates 
Ireland from the Pyrenees. They are probably trans- 
ported freely by migrating birds, either on their feet or in 
their feathers ; but the moist-soil species must also have 
been carried in profusion in the cakes of mud which adhere 
to the flanks of oxen that have rested in a moist meadow 
till the earth has dried on them. Before fences were made, 
the migrating horses, oxen, and bisons, in this way must 
have carried such seeds for long distances, and any adhering 
to the head of an animal would be carried across an arm 
of the sea uninjured. It must be remembered, however, 
that the autumn migration of mammals, which is the 
migration when nearly all the seeds are ripe, would have 
been southward in Britain,and consequently could only carry 
plants in that direction. The northward migration taking 
place in spring, few seeds would be carried, except such as 
had become entangled in the fur and were shed with it 
next summer. Wading and swimming birds, on the other 
hand, commonly come to Britain from the north and east 
in autumn, leaving the colder districts at a time when the 
seeds are ripe, thus bringing the smaller ones to this 
country. This is probably the reason why so large a pro- 
portion of the minute-seeded Arctic plants are found in 
Britain, though many of the species only occur in small 
numbers and at various scattered localities. 
The next group, that containing the plants with large 
edible unprotected seeds, is a small one in this country ; 
but it is of especial importance on account of the difficulty 
the species present when we try to account for their pre- 
sence in these Islands, except on the hypothesis of a former 
