294 NATURAL HISTORY OF THE FARM 
to find a place on some disturbance of existing condi- 
tions. A muskrat or a mole upheaves a mound of earth, 
and the seeds of these annual weeds, falling into this 
unoccupied soil, flourish there for a season ere the root- 
stocks of more permanent perennials again invade it. The 
annuals of the swale are quick-growing things, that depend 
for their success in the world upon their ability to shift 
from place to place, to find new openings, and to get in 
and mature a crop of seeds before the perennials crowd 
them out again. 
There are many beautiful and interesting flowers in the 
swale: yellow flowers, such as Saint John’s wort, buttercups, 
goldenrods and loosestrife; blue flowers, such as monkey- 
flowers, lobelias and gentians; white flowers, such as meadow- 
rue, turtleheads, avens and cresses; pink flowers, such as 
cockle-mint, willow-herb, fleabane and marshmallows; red 
swamp-lilies and flaming scarlet cardinal-flowers; and others 
in great variety and in continual succession. Formslikethose 
that grow on shoals (mentionedon page 35) willappearif there 
be permanent open water. Indeed, a careful study of even 
a small swale might discover the presence of a hundred or 
more plant species. ‘Ten or a dozen of these are likely to be 
found to comprise the greater bulk of the plant population. 
The dominant species are mainly those having comparatively 
simple and inconspicuous flowers, whose pollen is distributed 
by winds. The dominant species extend their domain chiefly 
by strong vegetative offshoots, occupy the soil with strong 
roots, and never let go. 
