Fig. 22. By yearly mowing and trampling the beaver meadow (Cala- 
magrostis association) is perpetuated, yielding a heavy and valuable hay 
crop. 
Fig. 23. Pine heath vegetation on the well drained sand plain at Platts- 
burg, N. Y. Pitch pine is becoming dominant over the heath shrub and 
sweet fern association. The previous virgin forest on this site was doubt- 
less white pine. 
