1905] LIVINGSTON—RELATION OF SOILS TO VEGETATION 4I 
the distribution of surface soils and the distance below the surface 
of the ground water level. 
It is probable that many dry soils may at length become moist 
enough to support one of the more moisture loving types of vegeta- 
tion, simply by increase of humus content, which must go on slowly 
at first but more rapidly as the amount increases. This is merely 
an application of one of the general principles of forest succession 
pointed out by WHITFORD (/oc. cit.). 
\ The lowlands are covered with a vegetation complex of species 
iuch that they can bear excess of water and paucity of oxygen in 
ae soil. From the open meadow and coniferous swamp we pass, 
tvith better and better drainage, through the mixed swamp to the 
flardwood or the white pine of the uplands. 
} It appears that the natural reforestation of the pine areas, with 
‘Norway pine, and to some extent at least with white pine, will take 
place if the fires can be suppressed. 
THE UNIVERSITY OF CHICAGO. 
Note.— Since the preparation of this paper, a similar conclusion has been 
ached in regard to sterility in agricultural soils by WHITNEY and CAMERON, 
ull. 22, Bureau of Soils, U.S. Dept. Agric. 1903. Also, it has been shown by 
‘actual field test that coarseness of soil particles alone can produce sterility in spite 
lof a plentiful supply of water. See LrvincsTon and JENSEN, An experiment on 
jthe relation of soil physics to plant growth. Bor. Gaz. 38: 67-71. 1904. 
¢ 
