1920] — Wherry,—Soil Tests of Ericaceae and Other Families 35 
times as much acid as is contained by water is called " minimacid;" 
one containing from 10 to 100 times, * subacid;" from 100to 1000 times, 
“ mediacid;" and more than 1000 times, *superacid." Corresponding 
terms are used on the alkaline side, although medialkaline and super- 
alkaline soils are not known to exist in the eastern United States, to 
which these studies are confined. It is sometimes convenient to 
group together minimacid, neutral and minimalkaline soils under the 
term, * cireumneutral. ” 
As to the correspondence between these and previously used terms, 
—“oxylophytes,” as defined by Warming and others, seem to be 
characteristic of soils possessing only the higher degrees of acidity 
as here classified. * Calciphiles" or “calcicoles” may grow in soils 
of widely varying reaction, for calcium often exists in soils in the form 
of neutral salts, suchas the sulphate and the chloride. However, 
since a very abundant compound of calcium, the bicarbonate, yields 
an alkaline reaction, calcicoles are particularly frequent in alkaline 
soils. "These relations are brought out in the following table: 
TABLE I. COMPARISON oF Common Soin, Reactions AND PLANT TYPES. 
f LI . . T p . . 3 i . 
e acil Mediaid] Sabine Minimacid |Neutral | Minimalkaline 
us Cireumneutral 
Catctum Sarrs | Insoluble Sulphate, chloride, ete. Bicarbonate 
Absent | Absent 
Common| Common 
OxYLOPHYTES Common |Occasional | Rare 
CALCICOLES Absent |Rare Occasional 
For practical purposes, then, oxylophytes may be regarded as 
plants characteristic of mediacid soils, and calcicoles of cireumneutral 
soils. 
The tests are made by stirring up a soil with neutral water, pouring 
off the more or less clear liquid, and adding a drop or two of approp- 
riate indicator solution. From the color then assumed the specific 
acidity or alkalinity of the soil in question can be determined. Sets 
of indicator solutions arranged for use in the field, with directions for 
their application, can now be purchased. (See advertising columns 
of this journal). i 
Every species of plant has of course an acid and an alkaline limit 
to its growth; and if these are sufficiently wide apart the plant may 
be regarded as indifferent to soil reaction. In the Ericaceae and other 
families here studied, however, it has been found that not only do 
