119 
Whitney states in this connection (see p. 51) that I have "called attention to an 
apparent exception to his rule (that production is sensibly proportionate to the water 
supply) in the ease of heavy adobe (heavy clay) and sandy lauds in California which 
'bear equally good crops of wheat." It happens that this "exception" holds good 
throughout the somewhat extensive arid region of the United States; and my expla- 
nation is not only, or mainly, that the roots go deeper, hut that in the arid region 
soils are, as a rule, quite as rich in plant food (again by chemical analysis of the 
rejected sort) as the clay soils. Hence the abundant and lasting production of the 
arid sandy lands (even drifting sands) when irrigated. 
The argument that even the rich arid soils can not yield more than the maximum 
crops in the humid region can hardly be taken seriously. 
It is a striking fact that in the entire bulletin only a single full-soil analysis (i. e., 
one made with strong acids) is quoted. There is a table giving the results of deter- 
minations of available plant food, determined by the official method, alongside of 
the distilled-water extract, and it is apparent that the two differ widely. But there 
is no definite agreement among soil chemists as to the "available" determinations, 
whether as to value or method; the matter is still in the tentative stage, and I wholly 
dissent from the "official prescription." The table in question proves nothing. But 
it would have been instructive, so long as Whitney wishes to disprove the value of 
soil analysis as usually made, to have at least some of the soil classes he adduces as 
proofs analyzed by the usual methods, if only in order to show that these soil types — 
the Cecil clay, the Sassafras loam, Norfolk sand, etc. — are really, as alleged by him, 
the same soils over the area assigned to them. How have these soils been identified 
in the mapping? We are informed (p. 8) that "the classification of soils in the sur- 
veys made by this Bureau is based mainly on physical differences apparent to a 
trained observer." It it apparent from the annual reports that the mineralogical and 
geological data, which are elsewhere considered as essential to a definite characteri- 
zation of a soil, and which certainly are to be counted among the physical charac- 
teristics, are in most cases wholly ignored. Instead, we have local names by the 
thousand, conveying no meaning whatever to those not acquainted with the localities, 
since nothing but a scantily interpreted physiological analysis is ordinarily given. 
Even when the mineral composition of the soil, is obvious, these meaningless local 
names are retained against preexisting local or descriptive designations. Thus, we 
have, e. g., a "Fresno sand" appearing also in the report on Orange and Monterey 
counties, Cal., localities hundreds of miles apart. To the uninitiated only the phy- 
sical analysis is offered as a mark of their identity by the trained observer. It seems 
a pity that that training should not have extended to calling that material a granitic 
sand, which would have rendered the designation intelligible all over the world, at 
the same time conveying important practical information in view of the well-known 
cultural characteristics and value of granitic soils. It is given out that these studies 
will be made later in the laboratory. But it may be seriously questioned whether it 
would not be better to cover less ground more thoroughly and be content with less 
extended and less hasty mapping. This superficial method of work naturally excites 
criticism, not only at home but also abroad." 
Until some better proof of identity is shown we can not accept Whitney's conclu- 
sions, based on the similarity of the soil solution, with widely varying production on 
"the same soil;" and his entire argument suffers seriously from the absence of any 
convincing proof that "rich" soils do not supply plant food, even in aqueous solu- 
tion, more rapidly than does "poor" land. 
But is the aqueous solution the only source of supply? Whitney rejects in toto the 
idea that anything but the carbonic acid secreted by the roots aids the solution of 
plant food; but his method of analysis practically ignores even this solvent, the use 
of which was suggested and actually carried out by David Dale Owen, and tried by 
myself in the early fifties. I found it unsatisfactory and abandoned it; but it would 
seem to have been incumbent upon Whitney and his coworkers to introduce this 
inevitable agency into their soil extractions, if it was intended to represent natural 
conditions. 
But there is still a wide difference of opinion in this matter of the acid-root secre- 
tions, and the investigators quoted by Whitney have by no means settled the matter. 
Among others, Kossowitch,* when observing the fact that much calcic bicarbonate 
leached from his vegetation pots, failed to establish the absence of organic acids from 
the solution. The old etching experiments have not, to my mind, lost their force; 
and in my experience I find it difficult to overcome the evidence of litmus paper 
reproducing a faithful image of citrus roots (in the soil) filled with an 83-per-cent 
aCentbl. Agr. Chem., 32 (1903), p.' 143. 
6 Ann. Sci. Agron., 2. ser., 1 (1903), p. 220. 
