ROTATION OF FORESTS 



223 



bushes and gain the mastery. Sometimes the area grows 



to poplars or birches, and people wonder why the origi- 



nal forest trees do not return; but these forest trees may 



be growing unobserved here and there in the tangle, and in 



the slow processes 



of time the poplars 



perish for they are 



short - lived and 



the original forest 



may be replaced. 



Whether one kind 



of forest or another 



returns will depend 



largely on the kinds 



which are most 



seedful in that 



vicinity and which, 



therefore, have 



sown themselves 



most profusely. 



Much depends, 



also, on the kind 



of undergrowth 



which first springs 



up, for some young 



trees can endure 376 ' The farmer mows P art 



more or less shade than others. Figs. 373 and 374 show 



two stages in the return to forest. 



364. Pasturing and mowing tend to keep an area in 

 grass. This is because the grass will thrive when the tops 

 are repeatedly taken off, whereas trees will not. Note 

 that the wild herbs and bushes and trees persist along the 

 fences and about old buildings, where animals and mowing 

 machines do not take them off. A sod society means graz- 

 ing or mowing. Consider Figs. 96, 375, 376. The farmer 



roadside. 



