324 WISCONSIN STATE AGRICULTURAL SOCIETY . 
zones. Nature has made experiments on this subject, and has 
found it possible to raise them from Virginia to the British pos¬ 
sessions. Wisconsin lies centrally within this zone. 
The value of studying the natural distribution of this plant, to 
all who engage in this industry or possess lands suited to it, is then 
evident. A similar, though less conspicuous value attaches to the 
study of the native areas of our other plants. The geological sur¬ 
vey is attempting to put information on this subject in an avail¬ 
able form. 
From the vegetation, much may be inferred in respect to the 
soil. But this does not diminish the value of direct operations 
upon its nature. These observations, to be of permanent value, 
should be made upon subsoils rather than upon soils proper—or, 
at least, the purely surface characters should be set aside. This 
should be done for two reasons; first, because the surface soil is 
subject to so many local and changeable influences, and has been 
so much modified by cultivation and other artificial causes, that 
observations upon typical or “ virgin ” soils is scarcely possible, 
and secondly, because the future of our agriculture depends, not 
upon the present soil, but upon the subsoil, for winds, waters and 
cropping are rapidly sweeping the surface away, and but a com¬ 
paratively few years will pass before our present subsoil will be 
at the surface, and for the further reason, that the power of the 
surface soil to retain the strength it has, and to draw mineral re¬ 
source from below is most evidently dependent upon the subsoil. 
A series of such observations has been made during the present 
season and the results embodied in this map. [The map showed 
in colors the areas occupied by the prairie loam, the lighter marly 
clays, the heavier marly clays, the real clay, the sandy soils, and 
the peaty soils.] If we compare the areas occupied by these vari¬ 
ous soils with those covered by the several kinds of vegetation, 
we shall find a marked correspondence between them. The 
heavier marly clays, with a portion of the real clay, are covered, 
in general, by the maple and its associates. The lighter marly 
clays and a portion of the red clay are covered with oak openings 
and forests. The sandy soils, chiefly by pines to the northward 
and by oak openings and prairie elsewhere. The prairie loam, by 
the well known vegetation that gives it its name, and the peaty 
