294 NATURAL HISTORY OP 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. Forms like those 

 that grow on shoals (mentioned on page 35) will appear if 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. 



