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U.S. DEPARTMENT OF AGRICULTURE.

Report No. TAS

SOILS AND VEGETATION.

THOMAS H. KEARNEY, Assistant Puystovoerst,

Division of Vegetable Physiology and Patholog
, y i Gy Gy,

AND

FRANK K. CAMERON, Son. CHEemisgy,

Division of Soils,

WASHINGTON:
GOVERNMENT PRINTING OFFICE.
1902.
2

S44.

SOME MUTUAL RELATIONS BETWEEN ALKALT

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V. P. P.—90. 8.—44.

U. S. DEPARTMENT OF AGRICULTURE.

Hteport No: 71.

/

SOME MUTUAL RELATIONS BETWEEN ALK ALL
SOILS AND VEGETATION,

BY

THOMAS H. KEARNEY, Assistant PHysIoLocist,
Division of Vegetable Physiology and Pathology,

AND

FRANK K, CAMERON, Sor. CHeEmistT,

Division of Sorts,

WASHINGTON:
GOVERNMENT PRINTING OFFICE.
1902.

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LETTER OF TRANSMITTAL.

U. 8S. DEPARTMENT OF AGRICULTURE,
DIVISION OF VEGETABLE PHYSIOLOGY AND PATHOLOGY,
Washington, D. C., June 24, 1901.

Str: I have the honor to transmit herewith several papers on Some
Mutual Relations between Alkali Soils and Vegetation, prepared by
Mr. Thomas H. Kearney, of this Division, who was detailed to the
work at the request of the Chief of the Division of Soils, and Dr.
Frank K. Cameron, of that Division, and respectfully recommend
their publication as Report No. 71 of the Department. The studies
so far made in connection with the work discussed in these papers
have brought to light some important facts and have opened lines of
inquiry which promise to develop methods of dealing with alkali soils
that will reduce their injurious effects on crops grown where such
soils exist.

Respectfully,
ALBERT F. Woops,
Chief of Division.
Hon. JAMES WILSON,
Secretary of Agriculture.
3

LETTER OF SUBMITTAL.

U.S. DEPARTMENT OF AGRICULTURE,
DIVISION OF SOILS, ©
Washington, D. C., June 24, 1901.
Str: I respectfully submit herewith the manuscript of a report pre-
pared by Mr. Thomas H. Kearney and Dr. Frank K. Cameron to throw
light upon problems encountered by the field parties of the Division
of Scils in the soil survey of certain areas in the West affected with
alkali. As this is treated largely from the physiological side, it seems
proper that it should be transmitted by you for publication.
Respectfully,
MILTON WHITNEY,
Chief of Division.
Mr. ALBERT F. Woops,
Chie,*, Division of Vegetable Physiology and Pathology.
4

CONTENTS.

The Effect upon Seedling Plants of Certain Components of AlkaliSoils. By
THomas H. KEARNEY and FRANK K. CAMERON:

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Methods of experiment Se a gt a =
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Determination of the limit of endurance____-___- _-_.-__.-_-.-_----
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Concentration maximum permitting survival of the roots -____--_=
Concentration minimum prohibiting elongation of roots _____-_-_--
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Calcium sulphate and calcium carbonate in mixtures.______-_- ——
General significance of results with mixed solutions
Stimulating effect of dilute solutions
Economic importance of the results
Summary

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Bibliography

Formation of Sodium Carbonate, or Black Alkali, by Plants. By FRANK K.
CAMERON:

Introduction

Creosote bush
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Absorption of mineral constituents by the plant_..______--------------
Comparison of analyses
Summary

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Resistance to Black Alkali by Certain Plants. By FRank K. CAMERON:

Introduction __..

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Isolation and identification of acid exudation _____..._.__--_______-
iydroscopmie palt, on the plant surface... = -__- -. ».252- 2 Ae
Selective absorption of soil constituents __._.__..._......--.-.--...
Function of the acid exudation
Phosphorus in the plant
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Suaeda intermedia and Atriplex bracteosa

Summary

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SOME MUTUAL RELATIONS BETWEEN ALKALI SOILS
AND VEGETATION,

THE EFFECT UPON SEEDLING PLANTS OF CERTAIN COMPONENTS
OF ALKALI SOILS.

By THomaAs H. KEARNEY and FRANK K, CAMERON,
INTRODUCTION.

Everyone who is familiar with alkali soils knows that their charac
ter varies greatly,in different localities, one salt or combination of
salts predominating over others which may be present.' Sometimes
sodium carbonate, the dreaded ‘* black alkali,” is relatively abundant
as compared with the other soluble soil components. In other cases
this salt may be entirely absent or present merely as a trace, while
one or more of the ‘‘ white alkali” salts, e.g., sodium chloride or
sodium sulphate, plays the most important part.

It is also known that these salts are not all equally injurious to veg-
etation. Sodium carbonate, for instance, is generally believed to be
much more harmful than any other salt of common occurrence, owing
probably to its pronounced corrosive action on the plant tissues.
Gypsum, or the dihydrate of calcium sulphate, on the other hand, is
harmless and even beneficial in ordinary cases. Experiments with
solutions of chemically equivalent strength show very marked differ-
ences in the action of different salts upon plant growth. Hence the
question whether the salt forming the greater part of the soluble com-
ponents of a given soil is, to take a concrete case, the very injurious
sodium carbonate or the relatively harmless sodium chloride, may
often determine whether that soil is utterly useless or quite valuable
to the farmer.

It becomes, therefore, a question of great importance fo everyone
who is concerned with soils which contain an appreciable amount of
alkali to know definitely the relative harmfulness of the salts both
severally and in mixtures, since the latter is the condition under
which they almost invariably occur in nature.

Field observations will give some idea of how the soluble salt com-
ponents compare in this regard. But the conclusions are necessarily
somewhat vague and unsatisfactory; for in the field and under the
conditions that are found in nature it is practically impossible to study

1See Bulletin No. 17, Division of Soils, U. S. Department of Agriculture (1901).
7

8

the effect of any one soil component. It is rare indeed that the
‘‘alkali” is composed of but one salt or chemical individual. And,
as will be brought out later, it is entirely impossible to predicate

anything definite as to the action of a mixture of salts upon a plant
from a previous knowledge of the effects produced by each single salt. —

Conversely, it is equally impossible to draw conelusions as tothe action
of any one of a mixture of salts from observations of the effects pro-
dueed by the mixture itself.

The more exact methods of the laboratory are necessary in order to
give us precise knowledge, and with this end in view the present inves-
tigation was undertaken. It is not claimed that the results so far
obtained are inall respects conclusive. The fact that only two species
of plants were employed in these first experiments is sufficient indi-
eation that they are not. In physiological research nothing is more
dangerous than generalization from the behavior of one or a few
species of plants to that of plant life asa whole. It is a well-estab-
lished fact that species differ widely in their reaction to a given
chemical or physical condition. Witness the fact that seaweeds will
thrive in water containing 1.5 to 3 per cent of sodium chloride, and
that salt marshes, whose soil is saturated with water containing nearly
or quite as much of this salt, often support a luxuriant vegetation,
while the average crop. is killed by a much more dilute solution of
sodium chloride. Certain plants show a marked aversion to limestone
soils, while other species are almost entirely limited to soils having
a high content of lime.t’ But it is needless to multiply illustrations
of so familiar a phenomenon. |

That a similar diversity is manifested by different cultivated crops
in their sensitiveness to various mineral salts when present in the soil
solutions is well known. Therefore we can not safely predict, until
experiments with many different plants have been made, that the
order of harmfulness of the alkali salts here established for two plants
will be found to hold for all or even many of those which are com-
monly cultivated in the alkali regions. But, as it is obviously essen-
tial to the satisfactory prosecution of alkali soil work that a definite
standard for comparison of the salts be established, there need be no
further apology for the presentation of these first results of what it is
hoped will become an exhaustive investigation.

In the progress of the work numerous data were accumulated which
_ appeared to possess a more than ordinary degree of scientific interest,
especially as relating to the chemical theory of the dissociation of
electrolytes in solution and to the recently published hypothesis that
various salts, or rather their dissociated ions, enter into compounds

1 The interesting subject of ‘‘ lime-loving” and ‘‘lime-avoiding” plants has been
much discussed by European botanists. It is synoptically treated by Drude
(Handbuch der Pflanzengeographie, p. 51) and by Schimper (Pflanzengeographie,
p. 105). The latter author gives an extensive bibliography.

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with the proteids of the protoplasm of plants and animals, which ‘‘ion
proteids” play a highly important part in life processes and phenomena.
This aspect of the subject will be treated particularly in discussing
the significance of the experiments with mixed solutions.

METHODS OF EXPERIMENT.

SALTS EMPLOYED.

In the selection of a series of salts for investigation the experience
of members of the Division of Soils in field and laboratory served as
a guide. Salts were used which have -been determined as forming
definitely injurious components of alkali soils and as occurring in
sufficient quantity to be of practical importance. In about the order
of their general abundance in the Western United States these are
sodium chloride (NaCl), sodium sulphate (Na,SO,), sodium carbonate
(Na,CO,), sodium bicarbonate (NaHCO,), magnesium chloride (MgCl,),
magnesium sulphate (MgSO,), and calcium chloride (CaCl,). Inci-
dentally, experiments were made with gypsum (CaSO,2H,0), calcium
carbonate (CaCO,), calcium bicarbonate [Ca(HCO,),], and with
magnesium carbonate (MgCO,), and bicarbonate |Mg(HCO,).], as
well as with an aqueous solution of carbon dioxide (CO,), the last in
order to test a theory that suggested itself during the experiments
with carbonates and bicarbonates. .

In preparing and standardizing the solutions much assistance was
rendered by Mr. Seidell, of the Division of Soils.

The solutions were invariably made with salts manufactured by
Baker & Adamson, and found to be practically chemically pure, dis-
solved in distilled water.' They were made up in each case on the
basis of anormal solution—i. e., of a gram-equivalent per 1,000 ¢. c. of

'The water used in all experiments was distilled through a tin worm and was
collected and stored in Winchester quart bottles of practically insoluble glass.
A conductivity test showed this to be an unusually pure water, but in order to
establish this point beyond doubt, a portion of this same water was redistilled
from glass, the first and last portions being of course discarded. A. test of the
distillate showed it to possess about twice as great conductivity as that which
had been distilled only once from the tin. A comparison of cultures of lupines
in the water which had been only once distilled with that which was redistilled
showed practically no difference in the amount of growth made by the roots. As
Galeotti has lately shown [ Biol. Centralbl., 21, 329 (1901) ], the oligodynamic action
of relatively concentrated ‘‘colloidal ” solutions of metals disappears in the presence
of weak solutions of electrolytes. Thus a solution of copper containing 1 gram-
atom of metal per 126,000 liters of water produced no effect upon Spirogyra in
the presence of a 0.01 per cent solution of sodium chloride, and a solution of 1
gram-atom of copper per 63,000 liters of water acted only after twenty-four hours,
although in the absence of the electrolyte the toxic effect of the colloidal copper
solution is manifested at a dilution of 1 gram-atom of copper per 126,000,000 liters
of water. (See footnote, p. 50.) Hence it is practically certain that in the
experiments described in this report no complications were to be feared from the
possible presence of a trace of metals in the water used.

10

solution. In other words, in the case of monovalent compounds, one
gram-molecule was contained in a liter of solution, while in the case of
bivalent compounds, a half gram-molecule was present.' In this way
only is a really instructive and fair comparison of the effects of different
salts obtainable. Many experiments made in times past in which com-
parisons were based upon simple percentages of solute to solvent by
weight are for this reason of far less value than if normal solutions
had been employed. In order to study comparatively those effects
produced by different electrolytes which are not dependent upon
their respective chemical natures, but which are common to them all
and due only to their active masses (such, for instance, as effects due
to the osmotic pressure existing in the solution), it is obviously neces-
sary to take into consideration the number of reacting weights of the
electrolyte introduced and the amount of electrolytic dissociation
which takes place. That is to say, one must consider the concentra-
tion of the solution with respect to the number of reacting chemical
equivalents, molecules, or ions which may be present. Moreover,
attempts to study comparatively the effects produced by different
kinds of ions in the solution can only be made by approaching the
subject in this manner. But in all statements in this report of the
concentration of a given solution both fractions of a normal solution
and parts of salt to 100,000 of solution are given in order that the
results may be readily intelligible to readers who are familiar with
one or the other method, as the case may be.

The method pursued in these experiments was to make and care-
fully standardize a large volume of anormal solution of each salt
and then dilute to the required strength as occasion demanded.

In beginning the experiments the limit for each salt as determined
by investigators in the field was first tried, but immediately showed
itself to be too high. So lower and lower concentrations had to be
tested until the critical one was reached.

PLANTS SELECTED FOR EXPERIMENT.

For a variety of reasons the white lupine (Lupinus albus) was
employed in nearly all the experiments, although subsequently alfalfa
(Medicago sativa) was introduced for comparison. The lupine has a
seed of good size, averaging 10 to 12 mm. in greatest diameter. Asan
abundant supply of nutritive material is stored in the thick seed
leaves, there is no danger of starvation of the seedlings in experi-
ments of short duration such as those here deseribed. The lupine
seeds germinate readily, sending out a vigorous radicle with clean,

1Dandeno [Bot. Gazette 32, 229 (1901) ] has recently called attention to a certain
amount of confusion which has existed among both chemists and physiologists
as to the preparation of a normal solution, and it has seemed wise to describe in
detail the procedure followed in this investigation.

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bright, whitesurface. If the seeds are germinated in a proper medium
(sphagnum or peat moss saturated with water was actually employed)
the root is usually straight or nearly so. These characteristics are
important, as they permit the easy and accurate measurement which
is essential to a determination of the amount of growth made during
a given period. The white lupine has the further advantage of being
a favorite subject for experiment with plant physiologists, so that
numerous data for comparison are available.

In one series of experiments lupine plants were used which had
been grown for eleven days in a prepared culture solution, and had
not only developed a considerable root system, but had unfolded two
or three leaves in addition to the seed leaves. In these plants all the
processes essential to the life of a mature individual were undoubt-
edly in full activity. As a rule, however, a much earlier stage of
growth was preferred, as clearly affording a more sensitive index of
the effect of solutions. Experiments with older plants indicated that
they are less delicate registers of toxic effect. An additional advan-
tage in using very young plants is that they are practically independ-
ent of the substratum so far as food supply (that is, the mineral
ash constituents) is concerned, that stored in the thick cotyledons
answering all purposes. Consequently the confusion which would
unavoidably arise if a culture solution of several salts containing
the necessary elements of plant food were introduced is avoided by
the employment of seedlings.

Lupine seedlings were transferred directly from the sphagnum, in
which they had germinated twenty-four to forty-eight hours pre-
viously, to the solution in which the experiment was to be made. In
this stage of growth the seed leaves are still closely appressed one
to another, and are pale yellow in color. The initial root is 3 to
6 em. long, and shows as yet no indication of the appearance of lat-
eral branches. Care was taken to keep the moss so wet as to preclude
a normal development of root hairs; and in this respect the result
would be the same if the radicles had: been immersed in water imme-
diately after germination. It was desired to render as slight as possi-

ble the change of conditions in transferring from one medium to the

other. There is every reason to believe that under these circum-
stances the amount of injury sustained by the plants asa result of the
change of substratum was reduced to a minimum.’

' Wolf demonstrated [Landwirthsch. Versuchsst., 6, 203. (1864) | that plants which
had been grown in soil until a considerable root system was developed and then
shifted to an aqueous solution (as in the experiments of De Saussure and others)
could not be depended upon to give as satisfactory results as plants which had
been cultivated from the moment of germination in aqueous solutions. But in
the case of seedlings transferred from loose wet sphagnum to water before any lat-
eral roots had appeared no difficulty of this sort need be apprehended.

12

From the experiments of others with plants cultivated in salt solu-
tions it would appear that Lupinus albus agrees pretty closely in
point of sensitiveness with other large-seeded Leguminosa, e. g., peas
(Pisum sativum), beans (Phaseolus vulgaris), and, at least in some
‘eases, with the horse bean ( Vicia faba).!

In order to determine how closely plants of the same family corre-
spond in their resistance to toxic effect, and at the same time to
obtain data as to the behavior of a plant whose economic importance
in arid regions is inestimable, a number of experiments were made
with alfalfa (Medicago sativa). Here we have to deal with a plant
whose seeds are many times smaller than those of the white lupine
(1.5 to 3 mm. in greatest diameter). The radicle of the alfalfa seed-
ling is correspondingly small and delicate, and hence requires more
careful manipulation than does that of Lupinus. Alfalfa seeds were
germinated in wet blotting paper, and were transferred to the solu-
tions when the radicles were 1 to 2 em. long.

A basis for comparison of the effects of toxic solutions upon plants
of very different character and relationship is afforded by Heald’s
investigations of the action of extremely dilute solutions of hydro-
chlorie acid upon seedling peas, pumpkins, and maize.” This author
calculates that while one part of hydrogen ions (liberated by dissocia-
tion) in 6,400,000 parts of water killed the root tips of the pea (Piswm
sativum),® one part in 3,200,000 was required to produce a similar
effect upon the pumpkin (Cucurbita pepo) and one part in only
1,600,000 to destroy the root tips of maize (Zea mays). In other
words, maize offers four times and the pumpkin twice as much resist-
ance to the toxic effect of hydrochloric acid as do peas and lupines.

These results emphasize the importance of extending the present
investigations to other plants of as widely different botanical relation-
ship as possible. It is alsoof great moment that experiments be made
with different stages of growth of the same plant, from the germinat-
ing seed to some point near maturity. It is as certain that the same
kind of plant at various periods of development differs in its reaction
to a given salt solution as that the reaction of the same plant to the
same solution will be affected by variations of temperature and, per-
haps, of illumination.

1But not always, for True [ Annals of Botany, 9,372, (1895) |] found the white lupine
‘“‘more strongly affected by a 0.25 per cent solution than is Vicia faba by one of
1 per cent KNO, content.” He finds Pisum likewise more sensitive than Vicia
faba.

*Bot. Gazette, 22, 136 (1898).

8The white lupine appears to be about equally sensitive to H-ions, for Kahlen-
berg and True [Bot. Gazette, 22, 91 (1896)] determined its limit of endurance in a
solution of HCl to be ;55 normal, while later Kahlenberg and Austin jJourn.
Physical Chem., 4, 557 (1900) ] fixed upon ;2,, normal as a more accurate limit.

4Storp [Landwirthsch-Versuchsst., 13, 76 (1884)] found zine sulphate to be
extremely injurious to germinating seedlings when exposed to the light, but
harmless, or nearly so, in the dark.

13

The practical value of such a development of these studies is indi-
eated by certain conditions to which agriculture in alkali regions is
subject. It is well known that while at the beginning of the season
the salt components are often pretty equally distributed through a
considerable depth of soil and are in consequence comparatively harm-
less, the increased evaporation which accompanies increased temper-
atures and decreased atmospheric moisture as the season advances
draws these salts to the surface of the soil, where they often effloresce
and form ‘‘crusts” (especially in the case of sodium carbonate and
sodium sulphate). Hence older plants are frequently exposed to the
action of much more concentrated solutions than the same individuals
when younger had to contend with. Furthermore, the accidents of
irrigation may materially alter the alkali content of a soil in the midst
of the growing season of a crop. It is therefore to be hoped that this
important extension of the investigation may soon receive attention.

DETAILS OF MANIPULATION.

The manner of preparing the solutions and the plants to be culti-
vated has already been described. A few words about methods and
details followed in the experiments are in order.

To contain the solutions, glass vials nearly 3 em. in diameter and
holding about 70 c. c. of liquid were used. In the experiments with
lupines, only one plant was suspended in each vial by means of a hole
bored through a close-fitting thin cork stopper, the aperture being
entirely closed by means of cotton batting. Protection against undue
evaporation from the upper portion of the plant was secured by plac-
ing several vials in a glass jar containing a little water and inverting
another jar over the whole. The plant was so adjusted in the cork
that 1 to 3 em. of the terminal portion of the radicle was immersed in
the solution, the uppermost portion of the radicle extending through
the vapor-saturated space between solution and stopper, while the
hypocotylary section was invested with moist cotton.

In the case of alfalfa five or six plants were inserted in each vial in the
following manner: A piece of aluminum wire was passed through the
cork stopper in such a way as to allowit to be raised or lowered at disere-
tion. On the portion of the wire included in the vial five or six small
loops were made of proper size to hold in place each a seedling plant, with
its seed leaves resting on the loop and its root immersed in the solution.

The duration of the culture in the salt solution was generally lim-
ited to twenty-four hours, as it was usually possible at the end of that
period to determine accurately whether the root tip had been killed
ornot. Frequently, however, the plants were returned to the solution
for a second period of equal duration in order to remove all doubt
upon this point.' If at the end of that period no growth had taken

‘In this particular, as in others, the experimental methods outlined by Kahlen-
berg and True [Bot. Gazette. 22, 87, 90 (1896)] have been followed, as it was
desirable to make as close comparison as possible with their results.

14

place since the first examination, it was regarded as reasonably cer-
tain that the root tips had perished, and a less concentrated solution

was tried. To obviate the possibility of mistaking a temporary condi-
tion of plasmolysis for final loss of vitality the roots were in earlier

experiments transferred, after twenty-four hours, from the salt solu-
tion to distilled water; but this precaution soon proved to be need-
less. In all the experiments a control culture in distilled water was
maintained under conditions of temperature and illumination iden-

tical with those of the salt cultures. As a matter of course, the growth |
of the roots is by no means as rapid in distilled water as in ordinary

river water or in a prepared culture solution. ©

It was sought to keep the external conditions as nearly as possible |)
uniform during the entire series of experiments and a temperature of |

19° to 21° C. was maintained in the laboratory.!

The rate of growth during the period of experiment was ascertained {
by marking the radicle with india ink just before placing it in the solu- |

tion. The mark, which was made as fine as was compatible with per-

manency, was placed at a distance of 15 mm. from the root tip in the ease |
of the lupines and 10 mm. in the case of alfalfa (Medicago) so as safely |
to include the entire zone of active growth in the primary root.” This:
method of measuring the growth of roots was employed by Sachs in}
his classical studies upon the growth of primary and lateral roots,’ and |
has been widely adopted by plant physiologists. | By comparison of |
the marked root with a ruled surface the amount of growth during:
any given period can be determined with all the accuracy necessary |

in experiments of the kind here described.°

By using a considerable number of individual plants in each experi- |
ment with each solution (usually five in case of Lupinus and ten or
twelve in case of Medicago) it is believed that the variant due to
individual differences in vigor has been practically eliminated.”

1Jn this connection Klemm [Jahrb. f. wiss. Botanik, 28, 659 (1895) ] calls atten- |
tion to the great variability exhibited by plants as to their limit of endurance in |
solutions of acids of definite concentration if other external conditions be varied. |
Askenasy [Ber. deutsch. bot. Gesellsch., 8, 61 (1890) ] describes the effect upon the '
growth of roots produced by different temperatures or by a variation of temper- |

ature during a limited period of time.

? Sachs determined the length of the growing portion, in the case of roots of |
other Leguminosz, to be 8 to 10 mm. for Vicia faba and 3.5 to 6.5 mm. in Pisum |

sativum. [Arb. d. bot. Inst. Wiirzburg, 1, 413 to 419 (1873); Gesammelte Abhandl.,
2, 803 (1893) ]

3Gesainmelte Abhandl., 2, 778.

4For example, Kahlenberg and True use this method in all their experiments
with plants in solutions of toxic substances. [See Bot. Gazette, 22, 88 (1896) ]

>Askenasy [Ber. d. deutsch. bot. Gesellsch., 8,64, (1890) ] shows that this method of
marking causes a retardation of growth during the first hour thereafter, but that
this is overcome after two hours.. Consequently the method could be used with-
out hesitation in these experiments, although it is sometimes attended by disad-
vantages when the phenomena of growth itself are studied.

6More than 2,500 seedlings of Lupinus albus and 700 of Medicago sativa were
employed in the whole series of experiments.

“15

Indeed, that this was the case was pretty effectually shown by several
repetitions of the experiments with most of the solutions. It is also
indicated by the general regularity with which toxic effect is shown
to increase with every increase in concentration of the solution of
each salt. By several times repeating experiments with solutions
of approximately the critical strength the above-mentioned source of
error due to fluctuations in temperature, etc., was likewise reduced to
a minimum.

DETERMINATION OF THE LIMIT OF ENDURANCE.

In ascertaining the degree of concentration of a given salt solution
which will just permit the root tips to retain their vitality during the
period of experiment, one must of course be able to determine also
the point at which death definitely occurs. The death point is evi-
dently to be sought far below the degree of concentration which per-
mits no elongation whatever to occur during the period of experi-
ment, for often radicles, of which the marked zone had increased in
length several millimeters (even 6) at some time during the experi-
ment, were indubitably dead at the end of twenty-four hours.! The
mere fact of elongation, irrespective of the time in which it has taken
place, does not therefore determine the concentration of a salt solu-
tion in which roots will survive, although sometimes useful in ascer-
taining whether the root is absolutely dead at the end of a given
period. It is to the general condition of the apical portion of the
root that we must look for a criterion. While it is sometimes difficult
to describe those symptoms which denote the death of the root tip,
it is comparatively easy to recognize them after one has acquired
sufficient experience with the behavior of plants grown in toxie
solutions.

One of the most easily detected of the phenomena accompanying
death in plants is final loss of turgor due to excessive plasmolysis.
In other words, the tissues lose their water, and are unable to make
good the loss, even when restored to normal conditions. This is due
primarily to a change in the osmotic equilibrium of the plant cells.
Ordinarily, through the controlling activity of the protoplasm, a suffi-
cient osmotic pressure is maintained in the sap cavity of the cell to

1 Experiments were made with solutions of a strength known to be fatal, yet
permitting some elongation during twenty-four hours. Sodium sulphate (0.05
normal), sodium carbonate (0.02 normal), and magnesium chloride (0.05 normal)
were selected, and in every case it was found that elongation ceased entirely after
three to five hours. In a water control, on the other hand, growth was still pro-
gressing at the end of six hours, and an examination at the end of twenty-four
hours showed that it had been pretty equally distributed throughout the entire
period. These results as to toxic action correspond with Sachs’s statement [Land-
wirthsch. Versuchsst., 1, 219 (1859) ]; Gesammelte Abhandl., 1, 430 (1892)] that
‘‘roots appear to lose more and more the power of absorbing water containing
salt the longer they are in contact with it.”

16

retain the necessary minimum of water. But through various influ-
enecs, such as exposure of the tissues to a salt solution whose concen-
tration exceeds a certain limit, this power of adjustment may be
temporarily lost. In such cases a considerable proportion of the cell
- water diosmoses through the ectoplasm, and the protoplast in conse-
quence shrinks away from the cell walls, to which it is normally
closely applied. If the unfavorable condition persists, this tem-
porary plasmolysis may become permanent, and the cell is killed
outright. | ef

Such disorganization due to extreme plasmolysis can usually be
detected immediately by an examination of the plant tissues with the
microscope, and is one of the best indications of death.! Roughly,

however, injury of this nature is sufficiently indicated after a certain

lapse of time by loss of rigidity and elasticity in the plant or part of
a plant affected; in other words, it becomes flaccid. If, for example,
a root thus rendered flaccid by culture in a salt solution fails to regain
its turgor after being transferred to water or to a nutritive solution,
it may safely be considered as injured beyond recovery. This was
found to be the most satisfactory test of death employed.’

The color of the tissues is often a useful symptom of destructive
changes. Thus all the sodium salts employed, when given in suffi-

leThe only externally perceptible change [indicating death] is in many cases
collapse, amore or less strong, irregular recession of the protoplast from the cell
wall, which does not, however, accompany by any means all reactions of sub-
stances which occasion death.” [Klemm, Desorganisations-erscheinungen der
Zelle. Jahrb. fiir wiss. Botanik, 28, p. 657 (1895) .]

*Sachs [Arb. bot. Inst. Wurzburg, 1, 386; Gesammelte Abhandl., 2, 774] men-
tions as an indication of the approaching death of the root tip the disorganiza-
tion of the cells of the root cap, which becomes mucilaginous. This was noted in
many cases, but was not found to be a practical test of complete loss of vitality.
Another indication of injury to the apical portion of the root is a sharp bend
near the tip, which is very different from the normal gentle curvatures. This
usually appears where loss of turgor from plasmolysis is not manifested. While
indicating injury, this symptom by no means necessarily implies complete loss of
vitality and, therefore, does not serve our purpose as a symptom of death. Solu-
tions of a certain concentration of magnesium sulphate, magnesium chloride, and
calcium bicarbonate were found to produce this phenomenon in a marked degree.
In the case of the salt last mentioned the roots continued to grow slowly in dis-
tilled water, during a second period of twenty-four hours. True [Ann. of
Botany, 9,377, (1895) ] alludes to these ‘‘ sharp curves characteristic of injury.”

Another means of detecting loss of vitality in protoplasm, to which, however,
recourse was not had in the progress of this work, is its coloration when dead by
means of nigrosin, which does not color and does not injure living protoplasm.
See Pfeffer [Ueber Aufnahme von Anilinfarben in lebende Zellen. Unters. aus d.
bot. Inst. Tiibingen, 2, 268, 269], who found in experiments with roots of duck-
weed (Lemna) and with Spirogyra that nigrosin is not absorbed by cells while
alive. Living root hairs exposed for three days to a 0.5 per cent solution of this
stain assumed no coloration whatever, while hairs after death when similarly
treated readily absorbed it.

|

ey

17

cient amount, decolorized the tissues of the apical portion of the
root. This lost its normal brilliant white appearance’ and assumed
a lurid-whitish color. In the case of sodium carbonate (Na,CO,)
and of sodium bicarbonate (NaHCO.,) there occurred a marked clear-
ing of the tissues similar to that produced by the hydrates of potas-
sium and sodium, the root tips becoming nearly transparent. This
change is completed long before any loss of turgoris apparent. Mag-
nesium salts (chloride and sulphate) discolored the surface of the
roots, producing brownish spots which gradually spread over the
whole surface.? The difference in character of physiological effect
produced by salts of the same acid in the case of sodium on the one
hand, and of magnesium on the other, is very great when gauged by
these external appearances.

Another effect produced by some of these salts is an irregular
enlargement of a portion of the root. This is very marked in the
ease of calcium chloride, in a solution of 0.3 normal or thereabouts.
The root just above the tip develops a fusiform swelling of which the
greatest transverse diameter (2 to 5 mm.) lies 5 to 10 mm. from the
apex of the root. A less marked formation of this sort is sometimes
produced by magnesium chloride, and even by other salts.’

It is well to emphasize once more the fact that the death of the tip
of the primary root, and not that of the plant as a whole or even of
the entire root, was taken in these experiments as the indicator of the
toxie action of solutions. The condition of the distal 10 to 20 mm.

1 The ‘‘ shining white opaque appearance which is characteristic of all healthy
roots and which is due to air contained in theintercellular spaces.” (Sachs, Land-
wirthsch. Versuchsst., 1, 216; Gesammelte Abhandl.. 1, 427).

*Mettenius [quoted by Wolf in Landw. Versuchsst., 7, 202, (1865) ] found that
these spots, which appear on the roots of both the bean and maize when placed
in solutions of magnesium salts, are due to a coagulation of the contents of the
epidermal cells, which he did not, however, further describe. Wolf remarks that
they do not appear upon plant roots in magnesium salt solutions if a salt of potas-
sium, ammonium, or calcium be present.

Sachs (Arb. bot. Inst. Wiirzburg, 1, 411, 412: Gesammelte Abhandl., 2, 800)
describes swellings of apparently similar character which developed upon roots
grown in moist air and watered at long intervals. Wolf [Landw. Versuchsst., 6,
218 (1864) ] found that a concentrated solution of potassium sulphate acted in the
same manner. ‘The root tips soon swell in the solution: the form of the root
finally resembles that of the root of a tuber-bearing plant. Such swellings arise
in particular abundance where lateral roots will break through.” The action of a
one-fourth per cent solution of potassium nitrate upon roots of Lupinus albus as
described by True [Ann. of Botany, 9, 374 (1895)] is exactly similar to that of cal-
cium chloride. ‘‘ Swellings appeared near the tips and the ends tapered suddenly
to sharp points. On the other hand, the growth in thickness was much greater
than normal, the radicles above the swellings reaching the size of large radicles
of Vicia faba of the same length.”

8287—-No. 71—02——2 *

18

only was necessarily involved.'' In the more dilute solutions which
are still considered toxic, because destroying the root tip, the proxi-
mal portion of the root and the upper part of the plant are often not
conspicuously injured by twenty-four or forty-eight hours’ exposure.
After a certain lapse of time lateral roots are sometimes put forth
and grow vigorously in a solution (especially of calcium chloride)
which had killed the apical portion of the primary root.

This power of gradual accommodation on the part of the plant to a
solution which at first checked its growth.and even destroyed the
sensitive tissues of the root tip has often been remarked. It is buta
step from this to the well-known fact that by gradually increasing the
strength of a salt solution in which plants are cultivated they can be
made to endure a degree of concentration which would soon be fatal
if administered directly.* It follows that the limits of endurance here
recorded for Lupinus albus are merely those of its root tip, selected
as being the most sensitive indicator, and are in some cases lower than
the limits which would denote death of the plant asawhole. Further-
more, the limit of endurance for the entire plant could undoubtedly be
still further elevated by gradually increasing the strength of solution
in which the plants are cultivated.

But our present investigation aims merely at a comparison of ite
relative toxicity of the various ‘‘alkali” salts, to attain which the
simplest and readiest means are to be preferred. A standard for
further comparisons, rather than a thorough investigation of the
problem in all its ramifications, is the end of the present paper.

1This was likewise the objective of the experiments of Kahlenberg and True
[Bot. Gazette, 22,88, (1896)]. In order to obtain results closely comparable with
theirs, especially as bearing upon the hypothesis of electrolytic dissociation, their
mode of procedure has been closely followed in this as in other details. In advocacy
of this method of determining toxic action, Professor True writes: ‘‘ Repeated
experiments for years have convinced me that the method used gives the most deli-
cate and easily managed test that I know of for bulky objects like Lupinus roots.”

Coupin [Rev. Gén. de Botanique, 10, 177 (1898) ] criticises the work of Kahlenberg
and True. previously « uoted, to the effect that it is impossible to accurately deter-
m ne the to_ic limit of a solution in the short period of experiment (twenty-four
hours) allowed by thoseauthors. However, as Professor True observes, it was not
the point at which the who-e plant succumbs, but that which marks the death of
the zone of growth in the primary root, which formed the objective of his experi-
ments. Coupin’s method was to grow his plants for several days in the solutions -
to be tested, taking the strongest solution in which the plant as a whole continued
to grow after the first few hours as marking the limit of endurance (‘‘équivalent
‘ toxique’’). It is obvious, therefore. that no direct comparison is possible between
the results obtained by Coupin on the one hand and by Kahlenberg and True, as
weil as those here recorded, on the other, Coupin’s limits of endurance being
necessarily much higher.

* Thus Stange [Bot. Zeitung, 50, 292 (1892) ] found that root tips of Lupinus albus
and Phaseolus vulgaris soon died if exposed directly to a 0.5 per cent solution of
potassium nitrate, but by gradually increasing the concentration they could be
made to endure nearly 1 per cent without death of the protoplasm.

soe ee l,l ll

ay

7 a oe | a

19

RESULTS WITH PURE SOLUTIONS.
CONCENTRATION MAXIMUM PERMITTING SURVIVAL OF THE ROOTS.

By applying the methods and tests outlined above it was possible
to determine with a reasonable degree of accuracy the limit of concen-
tration for each of the salts in pure solution in which the root tips of
young seedlings of white lupine could just survive. It is believed
that, like conditions being maintained and the same plant in the
same stage of development being used, the limits will not be materially
altered by further experiment. Moreover, it is regarded as not improb-

able that the salts will be found toxic in about the order stated below

if other plants or other stages of growth of the same plant be tested |
with them. The limit of endurance in a solution of each particular
salt will doubtless be higher or lower for different objects, but the
general sequence of harmfulness should remain practically unaltered,
so far as the higher plants are concerned. Experience alone can
demonstrate the correctness of this assumption.

The limit of concentration permitting roots of white lupine to
retain their vitality during twenty-four hours is, for each of the more
important readily soluble ‘‘alkali” salts, as follows, the limit being
stated both in parts of salt per 100,000 of solution and in fractions of a
normal solution:

TABLE I.—Results of experiments with pure solutions.

Degree of concen-
tration.

Naine of salt. Parts per Fractions

00,000 | of a nor-
of solu- | mal solu-

tion. tion.
DS ye ae ee So ee a 7 0.00125
oy EXTeprirrahiye | erie ve Fost) ® Bae gee =e ee ee St a eee 12 . 0025
SL LIVE Ete DONTE» 25 ee eee a SS AS eS ee ee ee ee eee 26 - 005
SUMPTER SU MA bO (ots Seok eos oes a ok 5, SS OE ee ae ee 53 . 0075
Sea ChIOTIGS (6). -.25..2e~ oe ct ce 2 act CS ae Se ee ee a eee Sar 116 . 02
AGE ONT RIOT LONE ee pet nee ee te ke Jan che cum Soadwsedenue 167 .02
OEP ATPL EDL OT CE ee De a a a ee ee eee ee ee 1,377 B55

a — = — a

NotTeEs.—(1) With magnesium chloride the limit of endurance (for the whole plant), as deter-
mined by Coupin [Rév. Gén. de Bot., 10,188 (1898) ], is 0.8 per cent, while with magnesium sulphate
the limit is 1 per cent, thus reversing the order of toxicity for the two salts as given above.
Wolfe (Landw. Versuchsst., 6, p. 214) notes the strongly toxic effect of magnesium soiutions upon
roots of bean and maize. The brown coloration of the surface of the radicle. induced by these
salts, appeared afew hoursafter immersion. Wolf’s suggestion that the very poisonous effect
of magnesium sulphate may be due to the decomposition of the salt by excretions of the roots
can not be regarded as possessing great probability. His experiments, which were designed
primarily to ascertain the volume of water absorbed by the plant from solutions of various salts
of different concentration, are considered by him toindicate that the cell wall [ectoplasm] is
less permeable to sulphates than to other salts (1. c., p. 217). Loew (Bul. No. 18, Div. Veg.
Phys. and Path., p. 42) found that Spirogyra died after four or five days of immersion in a 0.1 per
cent. solution of magnesium sulphate, but remained alive for a long period in equivalent solutions -
of sulphates of potassium, sodium, and calcium. Similarly al per cent solution of magnesium
nitrate killed asmaller Spirogyra insix to twelve hours, while the nitrates of potassium, sodium,
and calcium, in solutions of corresponding strength, did not destroy the plant. The peculiarly
poisonous action of salts of magnesium described by Loew isexplained by him on the hypothesis
that calcium forms intimate compounds with proteids, and that these are essential to the organ-
ization and life of the cell-nuclei and chloroplasts of the higher plants. Consequently, if mag-
nesium is supplied without calcium to plants, especially in the form of readily soluble salts. such
as chloride, nitrate, and sulphate, the acids of the magnesium salts would be attracted by the
calcium which formed part of the nuclear proteidcompounds. The latter would consequently
be disorganized, magnesium being unable to take the place of calcium in proteid compounds
without fatal disturbances of equilibrium inthecell. Asevidence for this hypothesis isadduced
the corrective effect of the addition of lime to either soils or culture solutions in which plants
are suffering from magnesium poisoning, and the further fact that plants suffer less in culture
solutions from which both calcium and magnesium are absent than in such as contain magne-
ium but nocalcium. It must be observed, however, that the chemical rationale of this theory

20

rests upon the assumption that calcium isa stronger base than magnesium, and will exert a
greater attractive force upon acids, while it ignores the application of the mass law to the dis-
ibution of an acid between two bases, which itself accounts very satisfactorily for the facts
observed.

(2) Of sodium sulphate Wolf (Landw. Versuchsst., 6, pp. 210, 213) indicates that solutions of more
than 0.05 per cent are toxic to roots of the bean (Phaseolus vulgaris). Loeb [Am. Journ. Physiol-
ogy, 3, 393 (1900)], found sodium sulphate to be more poisonous than sodium chloride to eggs
of a fish (Fundulus heteroclitus). This he attributes to a precipitation of calcium from its ion
‘ proteid compounds in the protoplasm, a reaction effected through the sulphions dissociated by
sodium sulphate.

(3) The minimum toxic concentration for sodium chloride, the same plant and the same methods
being used, is placed about three times as high (one-sixteenth normal) by True [Amer. Journ.
Sci, ser. 4, 9, 187 (1901)]. As the experiments with sodium chloride here described were repeated
several times, without variation in the result, no explanation for this discrepancy is apparent.

Many experiments have heen made with sodium chloride as to its effects upon plants. It may
be of interest to refer to some of those in which limits of endurance have been determined,
especiaily as these are in all cases much higher than that given above for rcot tips of Lupinus
albus. Storp [Biedermann’s Centralbl., 13, 76 (1884) ] found that sodium chloride in a solution of
greater corcentration than 0.01 per cent retarded the germination ofseeds. Eschenhagen [Ueber
den Einfluss von Lésungen verschiedener Concentrationen auf den Wachsthum der Schimmel-
pilze (1889)], quoted by Stange in Bot. Zeitung (1892, p. 255), gives the following limits for the
active growth of fungi in solutions of sodium chloride and of sodium nitrate:

é Per cent | Per cent
Fungus. : sodium | sodium
chloride.| nitrate.

SPORES fc shee ceue ice seek ee snes kale ee aes oe ee eens aoe aera nee eee ee 17 21
Rennie) 2 = ss. cee dees tee oss Ssecnee scot cee sees seeee eee aia Pactatatays oiee aeaees 18 21
Botrybiset ane mestie cone la cece see ae ce ena consis es aici as mee eames ee ere eee 12 16

Richter [Ueber die Anpassung der Siisswasseralgen an Kochsalzlésungen Flora, 75, 4 (1892)]
found that Zygnema stellinum genuinum lived two months in a 6 per cent solution of sodium
chloride added to a culture solution, and_more than a_year when the sodium chloride solution
was. 2 per cent or weaker. De Freitag [Archiv fiir Hygiene, 11, 68 (1890)] is authority for the
statement that Bacillus tuberculosis lived three months, and the typhus Bacillus six months
in a saturated solution of sodium chloride. Coupin [Révue Gén. de Botanique, 10, 177 (1898)]
obtained the following limits for various plants in solutions of sodium chloride:

eae! Per Set
imit o in dif-
Plant. endur- | ferent

ance. | solution.

WAN GAL ie co eek seo ieee ato ee eee ce, aie sedi le e eeen e 1.8 0.5

TELE FS ac acs SIS oe a cn ER SCRA cy Se DRA 2 Ue ae A a oe 8 1.2 . 20
WhitodipinowsseU le a2 Se oe eee elas e sat ce eee cea ee eee see eee oe meee 1 2h) tos eee
VERT Cerne errata ce Bhs iS eile Siar eye ie ae ea ea ek oe ee 14 oleo 2 eee
RVG GC Tales iin a eh EE le Ss eo AS Oe a Oe eel ae pce ee a ys non Oe

According to W. Sigmund [Landw. Versuchsst., 47, 1 (1896)] the maximum concentration of
NaCl solutions endurable by germinating seeds of cereals is 0.5 per cent, of legumes 0.3 per
cent, of rape 0.1 per cent Loew [Bul. 18, Div. Veg. Phys. and Path., p.19] found that Spirogyra
suffers in a solution containing 0.5 per cent of sodium chloride.

(4) Carbonic acid (HCO3) is here regarded as a monovalent acid, so that a gram molecule
(instead of one-half of a gram molecule) to the liter has been used in making up normal solu-
tions of sodium bicarbonate. To prevent inversion to the normal carbonate (Na COs) [see
Cameron and Briggs, Bul. 18, Div. of Soils, 1900; also Jour. Physical Chem., 5, 537 (1901)] solutions
of the bicarbonate were always well charged with carbon dioxide and were tested for
hydroxyl with phenolphtkaleine before being used in culture experiments, and again at the end
of the experiment. It is quite possible, of course, that a small error was thus introduced, as the
carbonic acid formed by the dilution of carbon dioxide in water may have retarded somewhat
the dissociation or ionization of the sodium hydrogen carbonate. It is improbable that sodium
hydrogen carbonate, unaccompanied by the normal carbonate, would ever occur in nature
except in the presence of an excess of carbon dioxide, which fact is a further justification of
the procedure here described.

In order to demonstrate that this excess of carbon dioxide was not in itself injurious to the
roots of white lupine, the following simple check experiment was made: Carbon dioxide was
forced into distilled water until a saturated solution was obtained. Plants were then entered in
this solution, which was protected as completely from loss of carbon dioxide as circumstances
would permit. After twenty-four hours the solution was tested with barium hydrate, and the
heaviness of the resulting precipitate of barium carbonate showed that very much more carbon
dioxide still remained than is present in ordinary water. During this period the roots grew
nearly as well as in water containing only the normal quantity of carbon dioxide. It might be
supposed that a solution of carbon dioxide in water and presumably containing the. hypothet-
ical carbonicacid must needs be itself quite toxic, as it would be expected to yield the hydrogen
ion which recent investigations have shown to be excessively toxic. In this connection some
work of Pfeiffer [Ann. Chem. (2), 28, 625 (1884) ] will proveinteresting. This investigation showed
that a solution of carbon dioxide is an exceedingly poor conductor; that in fact the highest con-
ductivity observed in such solutions was only about a thousandth of that which Kohlrausch’s
work showed it should possess. See also Knox [Ann. Phys. Chem., 54, 44 (1895)] and Walker and
Cormack [Journ. Chem. Soc., 77, 5 (1900) ]. '

It would seem rational, therefore, to consider that carbonic acid does not exist itself, or at
least in only minute quantities in solutions of carbon dioxide, but is potentially present in its
constituents and only forms in the presence of some added influence,suchasa base. And that,
therefore, even a concentrated aqueous solution of carbon dioxide would contain no hydrogen
jones or so very small a quantity as to be ineffective against so delicate an indicator as a plant
root.

a
s

x

————— SC UF

21

Experiments to ascertain the limit of endurance in pure solutions
were also made with seedlings of alfalfa (Medicago sativa). Althouga
absolute limits for this plant have not, as yet, been determined, they
appear to be somewhat lower for every salt than inthe case of Lupus
albus, but more than one-half as high. Thusfor magnesium sulphate
the limit appears to lie between 0.000625 and 0.00125 normal, while for
magnesium chloride the limit will be found between 0.00125 and 0.0025
normal.

A glance at the preceding table shows very clearly that it is the
basic rather than the acid radicle of the salts used which chiefly deter-
mines their relative toxicity. In other words, the cathions derived
from these salts are very much more active in their effect upon plant
tissues than are the anions. This is strikingly brought out by a
comparison among themselves of the three chlorides of magnesium,
sodium, and calcium, on the one hand, and of the chlorides and
sulphates of magnesium and sodium, respectively, on the other. In
the former case, although the anions (Cl) are identical in kind we find
magnesium chloride eight times as toxic as sodium ehloride, and one
hundred times as toxic as calcium chloride. In the latter case, mag-
nesium sulphate is only twice as toxic as magnesium chloride, while
sodium sulphate is little more than twoand one-half times as injurious
as the corresponding chloride.

The results with salts of magnesium, as compared with those of
sodium, confirm the results obtained by W. Wolf, Loew, and others
as to the strongly poisonous qualities of the former base.

All four of the salts of sodium with which experiments were
made are widely distributed and often very abundant in the alkali
regions of the western United States. As was to be expected, sodium
carbonate or black alkali was found to be the most harmful of these,
but it is not much more injurious than sodium sulphate. That the
latter is much more poisonous than sodium chloride is a result not
altogether anticipated at the beginning of the investigation.! As was
predicted, sodium bicarbonate proved to be somewhat less toxic than
sodium chloride.’

As a matter of fact, the limit of endurance in a solution of sodium
bicarbonate is not much higher in parts of salt per 100,000 of water

'Stewart [Ninth Ann. Rep. Utah Agr. Exp. Sta. p. 26 (1898)] found sodium
chloride more injurious than sodium sulphate to germinating seeds of legumes and
cereals.

’Very different results from these here recorded as to the relative toxicity of the
carbonate and bicarbonate of sodium were obtained by Coupin [Rév. Gén. de
Botanique, 12, 180 (1900)]. Experimenting with seedlings of wheat, this author
found that the least concentrated fatal solution (*‘ équivalent toxique”) is 1.1 grams
per 100 of water for sodium carbonate, while for the bicarbonate it is 0.6 gram.
Hence the latter would be twice instead of one-fourth as poisonous as the former.
Sigmund [Landw. Versuchsst., 47, 2 (1896) ] found that while Na,CO, at a concen-
tration of 0.5 per cent killed germinating seedlings of vetch and rape and retarded

' the development of wheat seedlings, NaHCO, at the same concentration was

harmless.

22°

and is no higher in fractions of the reacting weight than it is for
sodium chloride. It should be mentioned, however, that the plants
survive in a solution of the bicarbonate of the strength given in the
table in much better condition than in the corresponding concentra-
tion of the chloride, so that the latter must be regarded as the more
harmful of the two salts. The wide distribution of sodium bicarbon-
ate and its abundance as a component of many alkali soils renders
the demonstration of its marked poisonous effects upon vegetation,
even when present in comparatively dilute solutions, a matter of no
little importance. Although much less injurious than is the normal
carbonate or ‘‘ black alkali,” the presence of this salt can not be
neglected in future estimations of the value of western soils.

An explanation of the harmful action of sodium bicarbonate which
at first suggested itself was that by its dissociation free hydrogen ions
are liberated, though the weight of evidence on chemical grounds is
rather against this view.’ It has been shown by recent investigators”
that it is probably the hydrogen ions dissociated by certain acids
(especially the strong mineral acids) which make them so injurious to
organisms, even in extremely dilute solutions. If this were the reason
for the toxicity of sodium bicarbonate it would follow that water heavily
charged with carbon dioxide, as in the check experiment described
above (p. 20), would prove similarly injurious to plant roots by reason
of the dissociation of hydrogen ions by the carbonic acid (HCO,),
which is supposed to be formed when carbon dioxide is dissolved in
water. But, as has already been noted, no toxic effect was obtained
with an aqueous solution of carbon dioxide.’

1 Walker and Cormack, Journ. Chem. Soc., 47,5 (1900) and Bodlinder, Zeit. fiir
physik. Chem., 35, 25 (1900).

*Kahlenberg and True, Bot. Gazette, 22, 87 (1896); Heald, 1.c., p. 184; Loeb,
Pfliger’s Archiv f. die gesammte Physiologie, 69, 4 to 9 (1898); Kahlenberg and
Austin, Journ. of Physical Chem., 4, 553 (1900); True, Amer. Journ. Sci. ser. 4, 9,
183 (1900).

3 There exists among plant physiologists some diversity of opinion as to the direct
effect of large quantities of carbon dioxide upon the growth of roots. The sub- -
ject is evidently one which needs a more thoroughgoing investigation, not only
from a scientific standpoint, but from economic reasons also, as it is intimately
connected with tillage and drainage problems. For an extended discussion of this
question see Lopriore in Jahrb. fiir wiss. Botanik, 28, 531 (1895). “The author men-
tions that Boehm found roots of the bean (Phaseolus vulgaris), when exposed to
an excess of carbon dioxide, to be shorter, and the lateral roots fewer, than is
ordinarily the case. Jentys [Bul. Internat. Acad. Sci. Cracovie, 1892, 306 (1893) ],
found that by passing atmospheric air to which had been added 4 to 12 per cent of
carbon dioxide through the soil of culture pots, an injurious effect upon the roots
of the bean and the yellow lupine could be detected, although the injury was
less than in Boehm’s experiments. On the other hand, wheat was practically
unharmed. Lopriore (Il. c.,p. 623), concludes that carbon dioxide in excess has a
hindering but not a permanently injurious influence upon the functions of proto-
plasm. This effect is not ascribable to the absence of oxygen, but is specific.
Plant cells can gradually accommodate themselves toa quantity of carbon dioxide, ;
which, if applied directly, would injure them. Lopriore’s experiments were made
chiefly with Mucor, yeast, and pollen grains and tubes.

ve et eee

23

As there is probably but a small difference in the amount of sodium
ions yielded by sodium chloride and by sodium hydrogen carbonate,
at the dilutions here involved, the difference in their toxicity observed
must in all probability be ascribed mainly to the anions.

It is likely that the great toxicity of normal sodium carbonate is
largely due to the hydroxyl ions resulting from the hydrolysis of
this salt. In the case of the bicarbonate of sodium in all the experi-
ments involving its use, and described in this paper, hydrolysis was
avoided by dissolving carbon dioxide in the solution in amounts suf-
ficient to prevent any inversion to the- normal carbonate, a reaction
which would necessarily result were hydrolysis of the bicarbonate
permitted.’ Since it seems reasonably certain that HCO, ions are not
toxic,-the toxic influence of the sodium bicarbonate solutions could
be safely attributed to the sodium ion alone were it not for the fact
that toxic solutions of this salt produce the peculiar “‘ clearing” effect
upon plant tissues which is well known in the case of the normal car-
bonate of sodium and of the hydrates of potassium and of sodium.
This effect is very different from that caused by other salts of sodium,

e. g., the sulphate and the chloride.

Calcium chloride was found to be ten times less injurious than is .
sodium chloride. For this reason, and because it rarely predominates
in areas of any considerable size, this salt can not be regarded as,
under ordinary circumstances, a dangerous component of alkali soils.
As we shall presently see, there is reason to believe that it can in
many cases be a highly beneficial component of the soil.

Attention should be directed to the fact that the figures given in
the above table represent only approximate results, the determination
of the absolute limit for each salt depending theoretically upon the
‘testing of an almost infinite number of concentrations. Thus, as a
rule, solutions of a concentration of 0.2, 0.15, 0.1, 0.075, 0.050, ete.,
normal were employed, although more numerous intermediate concen-
trations, e. g., of 0.2000, 0.1825, 0.1750, ete., normal could have been
tested. However, it is doubtful whether the reaction upon plant
tissues of finer differences could be detected, and it is believed that
for all practical purposes a sufficient number of concentrations was
used. As has already been noted, the limits of endurance in the case
of different salts are not of precisely equal value, the roots not sur-
viving in all in exactly the same condition. Thus roots which survived
after twenty-four hours in a0.005 normal solution of sodium carbonate
presented a perfect appearance and grew vigorously in distilled water
during a subsequent period of twenty-four hours. On the other hand,
roots which endured a 0.25 normal solution of calcium chloride pre-
sented a markedly abnormal aspect at the end of twenty-four hours, and
made little subsequent growth when transferred to water. Likewise

1See paper on Equilibrium between Normal Carbonates and Bicarbonates in
Aqueous Solutions, Cameron and Briggs. Bul. 18, Div. Soils, U. S. Department
of Agriculture (1901); Jour. Physical Chem., 5, 537 (1901).

24

roots survived in better condition in 0.0075 normal sodium sulphate than
in 0.02 normal sodium chloride solution. It was found much easier to
determine sharply the limit of endurance for sodium carbonate and
sodium bicarbonate than for other salts, as in 0.005 and 0.02 normal
solutions of the two carbonates, respectively, all, or nearly all, roots
survived in apparently perfect condition, while in 0.0075 and 0.025
normal, respectively, all roots were killed and symptoms of advanced
disorganization were apparent after twenty-four hours.

CONCENTRATION MINIMUM PROHIBITING ELONGATION OF ROOTS.

A comparison of the seven salts above enumerated in regard to the
degree of concentration of each in which absolutely no elongation of
the roots occurred during twenty-four hours is interesting, as illus-
trating how far this point is removed from that of the minimum con-
centration which is still toxic. It will be seen that the position of the
salts in this scale does not at all correspond with their sequence in
the table of limits of endurance. In many eases, especially when the
solution was still more concentrated, not only no increase of length
but a positive shrinkage of 0.5 to 2 mm.! was detected.

TABLE II.—Concentrations which absolutely prevent growth.

_ Concentration of

solution.
Name of salt. Parts per
100,000 of | Normal.
solution.
Socmumicarbonate <2 oe statawos ae Semen. eee sa ae tee Se cate acts See ee er re eee ree 260 0.05
SOdimmMybiCahbOnate) neces 08 seo oe eee eee ae eee eee Ne lea ame 417 .05
Wi pneStU Tn CMLOMILG Gt. seca TM Ie SR eis Tar Oi See ee tm ne a emer 960 12
SoOdmmmMChlOride Goes 2 seas Se se See eee PD ee eg ee 1,160 .2
BOCES Uplate eso es Se ee eS a aa ee a ee eee ee DOL Es ah ae Sk pene 1,410 2
CAICIMMECHHORIGS ese eae a eae ce aes feet cae ie ape 1, 652 £3}
Mapnesiumr sulphates: occ foe ee ee i hs ae er 1, 680 .3

a According to Pfeffer (Pflanzenphysiologie, Ed. 2, 1, 414) a culture solution to which enough
potassium nitrate or sodiuin chloride is added to render it isosmotic with a 2 per cent potassium
nitrate or 1.7 per cent sodium chloride solution causes a cessation of growth in ordinary plants
while an increase to 3 per cent is necessary to prevent growth in halophytes.

It is impossible to reconcile this sequence, as compared with that of
Table I, with the notion, which still appears to find advocates, that the
injurious effect of these salt solutions is merely a function of their
osmotic pressures. If any fresh evidence were needed to disprove this
assumption it is afforded by the fact, very clearly brought out in the
present investigations, that marked toxic effects frequently appear
long before loss of turgor has manifested itself or cessation of growth
has occurred. It is certain that no useful conclusions as to the degree
of toxicity of a solution can be drawn from its osmotic pressure.

True [ Bot. Gazette, 26, 407 (1898) ] calls attention to the difficulty of
distinguishing the purely chemical from the merely osmotic (plasmo-

1TIn some solutions this loss of length due to plasmolysis was as great as that found
by Sachs in roots which were exposed for thirty minutes to the dry air of a room.
(Arb. bot. Inst. Wurzburg, 1, 396; Gesammelte Abhandl., 2, 784, 785.)

>

Nia Rw niet : . uk :
ee ath es ee ee et gee oe Siete iG

vee ae

lyzing) effect of a salt solution. He experimented with Spirogyra in
order to obtain means of making such distinction, comparing its
behavior in a solution of cane sugar, which is believed to possess no
chemically toxic properties, with that in solutions of sodium chloride
and potassium nitrate. The maximum concentration of the sugar
solution in which life could be maintained was determined to be 0.75
‘normal. Allowing for differences of dissociation, 0.46 normal should
then be the maximum endurable concentration of a sodium chloride
solution if only its osmotic pressure were involved. In fact, however,
0.1 normal was found to be the actual limit, so that a definite toxic
action of sodium chloride must be admitted (loc., cit., p. 410).?

Were the injurious action of these solutions attributable to plas-
molysis alone, an approximately equal amount of elongation should
take place in solutions of different salts, if each solution contain an
equal fraction of a gram equivalent to a given amount of water, grant-
ing that the dissociation of each salt was equally great at the given
concentration, as would be approximately true for strong electrolytes
at the concentrations here used; for elongation and growth in general
are intimately connected with the turgor conditions of the tissues,?
which, in turn, depend upon the osmotic force exerted by the sur-
rounding solution. That force being equal for each of two solu-
tions, the turgor and the amount of elongation of the roots immersed
in each should also be equal if osmosis were the only factor involved. -
That this is not the case is sufficiently established by the figures given
in Table II. :

RESULTS WITH LESS SOLUBLE SALTS.

Besides the easily soluble alkali salts a few others were used in
experiments, i. e., calcium sulphate [CaSO,] calcium carbonate
[CaCO,], calcium bicarbonate [Ca(HCO,),], and the carbonate and
bicarbonate of magnesium [MgCO, and Mg(HCO,),]. These were
found to be either toxic ina very slight degree, indifferent, or posi-
tively stimulating to growth.

‘From True’s results it is clear that at the concentrations involved in our experi-
ments with pure solutions the toxic effect observed must in every case be referred
to action of a chemical rather than a purely physical nature. In some of the
mixed solutions, such as the very concentrated ones containing calcium sulphate,
it may be that their osmotic pressure determines the limit of endurance of the
plant roots. :

* For example that, except perhaps in rare instances. growth can not be resumed
after an interruption (such as is occasioned by transference of plants from one
mnedium to another) unless the turgor of the plant or the organ concerned is nearly
or quite norntal, was shown by Curtis [Bul. Torr. Bot. Club, 27, 1 (1900)] in the
case of mycelia of Mucor, Botrytis, and Penicillium, grown in a plasmolyzing
solution (4 per cent potassium nitrate). As this author expresses it, ‘‘there isa
necessity of a certain turgor force before growth is possible, and growth can not
occur until a turgor pressure has been reached which is normal to the plant grow-
ing in the given solution.” (Loc. cit., p. 11.)

26

In a (necessarily dilute) solution of gypsum, which contained a con-
siderable quantity of the undissolved salt in suspension, the plants
grew decidedly more vigorously than in pure water.

In a saturated, but necessarily very dilute, solution of normal oa
cium carbonate [CaCO,], roots of Lupinus elongated nearly twice as
much and remained in decidedly better condition during twenty-four

hours than in distilled water. This-solution gave a faint reaction for —

hydroxyl (with phenolphthaleine) at the beginning of the experi-
ment, but none at the end of twenty-four hours, doubtless because of
the production of carbonic acid through the excretion of carbon
dioxide by the roots. But a solution of calcium bicarbonate
[Ca(HCO,),], made by saturating a portion of the same ealcium ear-
bonate solution with carbon dioxide, permitted only about one-third
as much growth of.the roots as took place in distilled water. Their
condition was decidedly Heenan at the end of twenty-four hours,
even the turgor being poor.*

Magnesium carbonate [MgCO,], in a solution which gave a strong
hydroxyl reaction with phenolphthaleine, allowed the roots to grow
about as rapidly as in distilled water and to remain in about normal
condition. On the other hand, a portion of the same solution to
which an excess of carbon dioxide was added and in which no free
hydroxyl could be detected (either before or after the experiment)
exerted a strongly toxie action upon the roots. These made practi-
cally no growth during twenty-four hours; their turgor became
decidedly inferior, and there occurred a marked discoloration of
brownish spots, such as is produced by the readily soluble mag-
nesium salts. Here it is obviously a case of a greater amount of
magnesium in solution, owing to the presence of carbon dioxide in

1 The stimulating effect which lime often exercises upon the growth of plants is
too well known to require illustration. The presence of calcium salts in consid-
erable quantity leads toa more vigorous production of root hairs than is normally
the case, as can easily be demonstrated by culture experiments, in which only the
tip of the root is immersed in the calcium salt solution. On the surface of the root
above the solution a great number of unusually long root hairs appear. To this
effect of the presence of lime, and the consequent readier absorption of potassium
and ammonium salts from the soil, Loew attributes in part the benefits obtained
by liming. (Bul. No. 18, Div. Veg. Phys. and Path., U.S. Department of Agricul-
ture, p. 43.) That calcium salts directly stimulate growth, apart from the produc-
tion of root hairs, is, however, shown by cultures with the root entirely immersed
in an aqueous solution, thus precluding any important development of these organs.

*Schloesing’s investigations [Comptes rendus, 74, 1552 (1872) ] showed that 100,000 -

parts of pure water, i. e., free from dissolved carbon dioxide, would dissolve about
1.3 parts of calcium carbonate. Treadwell and Reuter [ Zeit. fir anorg. Chem.,
35, 28 (1900)] showed that by increasing the pressure of the carbon dioxide in
the gas phase in contact with the solution until it was one atmosphere, the solu-
bility was increased so that 100,000 parts of water would dissolve 116 parts of
calcium carbonate. Even at this extreme solubility there would be but 46 parts
of calcium per 100,000 of water, as against about 60 parts in a saturated solution of
calcium sulphate, in which plants thrive well.

|

27

excess.' Why the corresponding calcium solution should also hinder
growth can not be satisfactorily explained at present.

RESULTS WITH MIXED SOLUTIONS.

Upon comparing the limits of endurance for lupine roots in pure
solutions of the ‘‘alkali” salts with the limits determined by the
methods employed in a field survey, it became obvious that the for-
mer were vastly lower than the latter; and that furthermore the order
of toxicity of the several salts as fixed by investigators in the field
differed greatly from that obtained by experiments in the laboratory.
This was strikingly the case with magnesium sulphate, which is
decidedly the most toxic of the seven salts when alone in a pure
aqueous solution, but which is regarded as the least injurious by
students of alkali soils. But it was recalled that none of these salts
usually occurs in any notable quantity in the soil save in the pres-
ence of one or several others, both of the readily soluble salts and of
the comparatively insoluble magnesium carbonate, calcium carbonate,»
and calcium sulphate. The key to the discrepancy appeared there-
fore to lie in mixtures of the various salts, and the study of these
became, logically, the next step in the investigation.

In experimenting with mixed solutions it was planned to test every
possible combination of two of the readily soluble salts with which
experiments were made in pure solutions. Another line of experi-
ments, from which were obtained results which are believed -to be of
considerable scientific interest and from an economic point of view
to indicate one of the possible solutions of the alkali soil problem, con-
sisted in combining each of the readily soluble salts with each of
three difficultly soluble ones—calcium sulphate, calcium carbonate,
and magnesium carbonate. The only triple mixtures so far tried are

_ those of each readily soluble salt (except calcium chloride) with eal-
cium sulphate and calcium carbonate. Sodium bicarbonate was
tested only in this triple mixture.

Although the work with mixtures of salts is by no means com-

1 Treadwell and Reuter [ Zeit. fir anorg. Chem., 17, 199 (1898)] showed that at
15° C. and under a partial pressure of carbon dioxide in the vapor phase equal to
zero, pure water dissolves about 63 parts of magnesium carbonate per 100,000.
With a partial pressure of carbon dioxide in the vapor phase equal to one atmos-
phere there was dissolved about 1,211 parts magnesium hydrogen carbonate,
equivalent to 698 parts of the normal carbonate per 100,000 of solution. It is thus
seen that the solubility is enormously increased by the presence of carbon dioxide.
Cameron and Briggs [Bul. 18, p. 22, Division of Soils, U.S. Department of Agricul-
ture (1900) ] showed that a solution of magnesium carbonate in solution in equi-
librium with ordinary air contained about 18 parts of magnesium in 100,000 of
solution, which might have been expected to be enough to prohibit growth in view
of the toxicity of solutions of magnesium chloride and magnesium sulphate. It

should be further noted that it was shown that 6 parts of the dissolved magnesium
was combined as the normal carbonate, so that the solution contained more than
appreciable-amounts of OH ions, resulting from the hydrolysis of this latter salt.

28

pleted, the data thus far obtained throw so much light on the whole
subject of alkali soils, and go so far to account for the fact that the
limits of endurance of plants in pure solutions of the various salts
are low as compared with those determined from the observations
of survey parties in the field, that it seems advisable to present
them here.

In the case of mixtures of two readily soluble salts, solutions of
each, of twice the desired concentration, were mixed in equal vol-
umes. Where one of the salts is a comparatively insoluble one, it
was added in solid form to a solution of definite concentration of the
soluble one, and the mixture was then diluted to the required con-
centration, as though the more soluble salt alone were present. (The
source of error incurred by this method was considered so slight as
to be practically negligible.) The mixture was then allowed to
stand for a week or ten days with frequent shaking, in order to bring
it to equilibrium before using. In all mixtures of magnesium ecar-
bonate and of calcium carbonate alone with other salts, the undis-
solved residue was removed by filtration. Likewise in earlier experi-
ments with calcium sulphate added to other salts, the residue was
removed, but in those upon which are based the limits given in the
tables it was retained. In all cases where both calcium sulphate and
calcium carbonate were added, the undissolved residue remained
during the culture. The difference in limit due to the presence or
absence of a solid excess was, however, wena imperceptible, and
always slight.

In every case the object was to ascertain how far the limit of endur-
ance for the roots in the presence of the more toxic salt could be
raised by addition of one that is less injurious. Although the con-
centration of solution of the latter is invariably stated, if it be a
readily soluble salt, it is the concentration of solution of the more
poisonous salt as denoting a corresponding limit of endurance to
which attention is chiefly directed. It is interesting that in cases
where both of the salts mixed are readily soluble ones the less toxie
salt appears usually to be more effective in neutralizing the more
toxic one when added in concentration somewhat above rather than
below that in which plant roots will endure it when alone. Thus, in a
mixture containing equal volumes of 0.0075 normal sodium carbonate
and 0.01 normal sodium sulphate, roots of two plants survived, but all
died when the mixture contained 0.0075 normal sodium carbonate and
only 0.005 normal sodium sulphate. Also a majority of the roots
could retain their vitality in a mixture containing equal volumes
of 0.0025 normal magnesium sulphate and of 0.01 normal ‘sodium
sulphate, but not in 0.0025 normal magnesium sulphate plus 0.005
normal sodium sulphate. Similar results were obtained by adding
sodium sulphate to magnesium chloride and sodium chloride to mag-
nesium sulphate. The reverse was true, however, in the mixtures of
magnesium chloride and sodium chloride, the less concentrated solu-
tion of the latter proving more beneficial.

29

The concentrations are stated, as in preceding tables, both in parts
of salt to 100,000 of solution and in fractions of a normal solution.

In the following tables of the effects of mixtures each of the more
soluble alkali salts (excepting sodium bicarbonate) is taken up in
succession in the order of its toxicity in pure solution. The neutral-
izing effect is expressed in terms of the greatest concentration of the
more toxic salt endurable in the presence of the less toxic one. As
the determination of the value of a less injurious salt in neutralizing
a more toxic one was the objective of all experiments with mixtures,
it follows that the number of added salts decreases successively from
table to table. For comparison, the limit of endurance for the more
toxic salt in pure solution is stated at the head of the table. The
details of neutralizing effect upon each salt are taken up in connec-
tion with its respective table, while a discussion of the general sig-
nificance of the whole series of experiments with mixtures of two
solutions is appended.

The results embodied in Tables III to [X were obtained from experi-
ments with Lupinus albus only. In Table X, however, the limits
are given for both Lupinus albus and Medicago sativa (alfalfa) in
solutions of each readily soluble salt (excepting calcium chloride) in
the presence of an excess of calcium sulphate and calcium carbonate
together.

MAGNESIUM SULPHATE IN MIXTURES.

The following table shows the results of experiments with Lupinus
in solutions of magnesium sulphate with other salts added:

TABLE IIl.—Limits for magnesium sulphate in mixtures.

Greatest endurable

concentration of Concentration of the
Magnesium sul- salts added.
phate.
Name of salt added.
In frac :
les In parts In fractions |In parts per
petete per 100,000 ofa normal, 100,000 of
tation. solution.| solution. | solution.
| |
Bn Fe ee ne a 0. 00125 (Pap a eee ss
Benes Chlgring =) Sas 2-5. . 000625 3.5 0. 0025 12
itmun cirbiiielger ts ee | 00125 | 7 0025 13
Sodium sulphate .--.--.-----..--- Jane -003875 | 21 -O1 80
ee |
UP USO BCE een eee ee ee ee 2 ; : .
mepmcwuin enrvonate —-~ 5 2.2 oe. .O1 56 | Saturated.| Saturated.
TE UTE CES CT ee ee a eee . 02 | 112 Saturated. | Saturated.
BSS (er a ee | 6 3, 360 Saturated. | Saturated,
Calcium sulphate and calcium carbonate ---.-. ae | 2, 240 Saturated. | Saturated.

Inthe light of figures given above, the enormous discrepancy between
the results obtained by experiments with this salt in pure solution and
the limit determined by field survey is completely obliterated. For
in alkali lands magnesium sulphate is rarely,if ever, found in any
quantity except in the presence of calcium sulphate; and it is com-
monly accompanied by both sodium and calcium sulphate (the Billings,

-_—

30

.

Mont., type of alkali soil’). Addition of sodium sulphate, which is
itself so injurious in a pure solution, raises the limit for magnesium
sulphate three times, while the presence of calcium sulphate allows a
small proportion of the roots to barely survive during twenty-four
- hours in a solution of magnesium sulphate 480 times as concentrated
as that which, in pure solution, represents the limit of endurance. A
careful comparison was made between 0.3 and 0.4 normal solutions of
magnesium sulphate, both in the absence and the presence of an excess
of calcium sulphate, five individuals of Lupinus albus being cultivated
for 48 hours in each of the four solutions. The following table gives
the results:

TaBLe [V.—Magnesium sulphate with and without calcium sulphate.

| Average
| elongation
Solutions. | suareede AS General condition of the roots.
| tion of the
| root.
i Millineters. |
Magnesium sulphate (0.3 normal) --...._-..--- 0.7 | Extremely flaccid, and discolored
with brownish blotches; extreme-
: ly plasmolyzed.
Magnesium sulphate (0.3 normal) + calcium 10.2 | Turgor normal; plasmolysis none;
sulphate. Sa roots quite badly discol-
ored.
Magnesium sulphate (0.4 normal) __......-_-.- .3 | About as in 0.3 normal.
Magnesium sulphate (0.4 normal) + calcium 13.0 | Turgor normal; plasmolysis none;
sulphate. Blt bat one root quite badly dis-
colored.

In both pure solutions the protoplasm of the nearly isodiametric
cells of the periblem was completely withdrawn from the cell wall and
collected with the nucleus in a compact mass near the center of the cell;
while in both solutions to which ealcium sulphate had been added
no trace of plasmolyzing action could be detected in the cells of the
periblem, the protoplasm being closely applied to the wall, with large
vacuoles in the older cells, and the nucleus usually peripheral. Pre-
cautions were taken while preparing the sections to keep the tissues
immersed in the culture solution, and the absence of plasmolysis in
the roots taken from the solutions containing calcium sulphate is
sufficient evidence that the pure solutions had produced this effect
during the period of culture rather than after withdrawal.*

1See Whitney and Means, Bul. 14, Div. Soils, U. S. Department of Agriculture
(1898), and Cameron, Bul. 17, p. 32, Div. Soils, U. S. Department of Agriculture
(1901).

2Wolf’s observation (see- footnote, p. 40) that both Ca (NO,), and Mg (NO,),
are readily absorbed by plant roots when mixed together, while neither is readily
absorbed from a pure solution, renders it highly probable that in this case of a
mixture of MgSO, and CaSO, it is the rapid endosmosis of the salts into the cells
of the plant roots which prevents plasmolysis of the latter.. In short this mixture
is to be compared with those substances described by Overton [Vierteljahrsschr,
Naturf. Gessells ch. Ziirich 40, 1 (1895) ] which produce only transient plasmolysis,
owing to their more or less rapid passage through the ectoplasm into the cell sap.
As determined by De Vries [Jahrb. fiir wiss. Botanik, 14, 537 (1884)], a 1.8 per
cent solution of magnesium sulphate (which would correspond to our 0.3 normal

. z. 81

In the presence of both calcium sulphate and calcium carbonate
added in excess to a solution of magnesium sulphate, the limit of
endurance is only two-thirds as high as when calcium sulphate alone
is added.

Calcium as the chloride has also a powerful effect in neutralizing the
toxicity of magnesium sulphate. But here the addition of a new
anion (Cl), besides the added cathion (Ca), seems to diminish the
beneficial effect of the latter, since the chloride, although a readily
soluble salt, raises the limit for magnesium sulphate only one-third as
much as does the little-soluble calcium sulphate. In a mixture of
ealcium chloride and magnesium sulphate a crystalline precipitate of
ealcium sulphate separates slowly or rapidly in proportion to the con-
centration of the solutions, so that the case becomes that of the
contact of solid calcium sulphate with a solution of magnesium echlo-
ride. As would be expected, the limit of endurance for magnesium
sulphate plus calcium chloride is the same as that for magnesium
chloride plus calcium sulphate (Table V).

Sodium salts are very much less effective in neutralizing magnesium
sulphate than are salts of calcium. In the case of sodium salts it is
the chloride which is most effective, so that here we seem to have a
beneficial effect of the anion aswellas of thecathion. Yet the absence
of any neutralizing effect when magnesium chloride is added to mag-
nesium sulphate shows that the Cl ions alone are ineffective.

In one case the addition of a salt with a common basic ion—i. e.,
magnesium carbonate—raises the limit of endurance in magnesium
sulphate eight times.’ By a simple process of. elimination, since
magnesium ions are ineffective in the form of magnesium chloride
when added to magnesium sulphate, although chlorine ions appear
to have in themselves some neutralizing value when added as sodium
chloride, we are compelled to attribute the beneficial influence of
magnesium carbonate to CO,, or more probably HCO, ions, a point to
which we will return in discussing the stimulating effect of dilute
solutions of sodium carbonate and sodium bicarbonate. Noteworthy
is the fact that caleium carbonate, although much less soluble than
the corresponding salt of magnesium, is twice as effective an anti-
dote for magnesium sulphate. This affords another striking proof of
the great efficacy of calcium as a remedy for magnesium poisoning.

solution), is the isotonic equiva'ent of a 0.1 normal solution of potassium nitrate,
which is usually taken as the unit in measurements of osmotic pressure of solu-
tions. True [ Bot. Gazette, 26, p. 410 (1896)] found that plasmolysis of Spirogyral
cells in a KNO, solution first appeared at a concentration of 0.25 normal. De
Vries’ results seem to indicate that the osmotic value of each component in a
mixed solution (of two or three salts) is equal to that of the respective compo-.
nent when present alone at the given concentration, a point not in Sogreche with
well-established facts.

'The roots barely survive in poor condition in a 0.01 normal magnesium sul-
phate solution plus an excess of magnesium carbonate; but in 0.005 normal magne-
sium sulphate solution plus magnesium carbonate some of the roots were perfectly
normal after a twenty-four hours’ culture. |

o2

MAGNESIUM CHLORIDE IN MIXTURES.

The results of experiments with magnesium chloride in mixtures
with other salts are shown in the following table:

TABLE V.—-Limits for magnesium chloride in miatures.

——

Greatest endurable :
concentration of Coneentrarien oe the
magnesium chloride. BER aS

Name of salt added. f
In frac In parts In fractions | In parts per
tions of a | per 100,000 f
normal | of solu- | £4 normal) 100,000 of
Solution oe solution. solution.
BINION wettest bade Bone cis re eS ane aaese 0. 0025 1 D6 ERR arate) Ac a Ue
Sootum carbonates... sets ee eee eee eee . 0025 12 0. 00375 19.5
Sodiumysulphates cetos eeao a eee scone eee OL 48 .O1 80
SodimmrchlOrid esses enisesee ceces None oases oe OL 48 . 02 116
wal cinmychloridies {22455 -- 6 Se eee es al 480 15 726
Magnesium) carbonate: <= 22. cess2- 2-22-55 = oe . 0025 12 | Saturated. | Saturated.
Caleumicarbonates >) == sus coe ese . 04 192 | Saturated. | Saturated.
Calemmysul phateeeeee..o2225 scoot seme oe ree 2 960 | Saturated. | Saturated.
Calcium sulphate and calcium car nadere pe be 2 960 | Saturated. | Saturated.

In the alkali soils of the Western United States magnesium chloride
rarely occurs in such large quantities as to be regarded as more than
secondary in importance.!

As in the case of magnesium sulphate, calcium is found to be much
more effective than sodium in neutralizing magnesium, but here eal-
cium chloride is relatively more effective than with magnesium sul-
phate, raising the limit for magnesium chloride one-half (instead of
only one-third) as far as does calcium sulphate. But calcium is much
less effective with the chloride than with the sulphate of magnesium,
as is evident from the relative efficacy of calcium sulphate in raising
the limits of endurance of the two magnesium salts. Hence we have
here another indication (as in the case of calcium chloride added to
magnesium sulphate) that chlorine ions by their presence lower the
neutralizing efficacy of calcium; although in the absence of the latter
base, magnesium chloride is only one-half as toxic as is magnesium
sulphate. While the beneficial effect of calcium sulphate upon mag-
nesium sulphate is decreased by the addition of an excess of calcium
carbonate, the presence of the carbonate does not affect the value of
caleium sulphate as an antidote to magnesium chloride.

While calcium carbonate is equally effective in raising the limits
of the two soluble magnesium salts (sixteen times), magnesium car-
bonate, which raised the limit of magnesium sulphate eight times,

1 Magnesium rarely makes its specific effects upon plant life felt in the ‘‘ alkali”
soils, owing to the omnipresence there of considerable calcium salts. In certain
areas of the Eastern States, notably in the so-called ‘‘ serpentine barrens” of Penn-
sylvania and Maryland, it appears to be relatively more important, probably
because it is.there present in excess oyer calcium, although the actual amount of
both, which may be present in the soil solutions at any given time, must be
extremely small.

33

has no effect upon magnesium chloride. As it appears to be neces-
sary to regard the HCO, ions as the effective element in the former
combination, we must conclude that these act beneficially in the
presence of Mg and SO,, but are powerless in the presence of Mg and
Cl. But as calcium carbonate is equally effective as an antidote to
magnesium chloride and to magnesium sulphate, it would follow that
the power of Cl ions to hinder the effect of HCO, ions disappears in
the presence of Ca ions, while, as already noted, Cl ions appear to
diminish the value of Ca ions as an agency for counteracting Mg ions.
Comparisons such as these show how difficult it is to attempt an
interpretation of toxicological phenomena in the light of current
chemical and physiological ideas. Possibly determinations of the
solubility and degree of dissociation of these different salts in mix-
tures may afford some clue to the numerous anomalies. On the other
land, it is difficult to see any justification for using the reactions of
organisms in determining the dissociation constants of electrolytes.
The many nonconcordant results recently described in the literature
ean hardly be regarded as throwing discredit upon the dissociation
hypothesis, but rather as demonstrating the unsatisfactory natune of
the method employed for the investigation in hand.

Sodium sulphate and sodium chloride are equally effective in rais-
ing the limit of magnesium chloride (four times). The former is more
effective, and the latter decidedly less so, than in the case of magne-
sium sulphate, so that the anions (Cl, SO,) and not alone the cathions
(Mg, Na) appear to make their influence felt in these cases.

SODIUM CARBONATE IN MIXTURES.

Table VI shows results of experiments with mixtures of other salts
with sodium carbonate:

TaBLE VL—Limits for sodium carbonate in mixtures.

| Greatest endurable .
i : Concentration of the
concentration of salts added.

sodium carbonate.
Name of salt added.

Fees a In parts In fractions In parts per

ndnnik | Pot 100.000 ofanormal 100,000 of

ee eee solution. solution. solution.
_ (iM SE et ee eee | 0.005. | rey [Seer eee | See ee tS
7 OTS SE ia cia a a | 0075 | 39 0.01 | 80
2 USTED ee ee eee . 0025 13 01 | 58
eR Te TUS 1 ee ee | 25 1,300 2 1,377
Magnesium carbonate_._____...- 2S ae gee i -O1 52 Saturated. | Saturated.
ESS eg Ue ee ee - 0075 | 39 Saturated. | Saturated.
7 DUG i ae a Se Se ae 03 156 Saturated. | Saturated.
Calcium sulphate and calcium carbonate --.--- . 03 156 Saturated. | Saturated.

As the above table shows, sodium chloride is ineffective as an anti-
dote to sodium carbonate; calcium carbonate barely raises the limit

8257—No. 71—02

34

of endurance, while magnesium carbonate merely doubles it. It is
interesting that magnesium carbonate should here be more effective
than the corresponding salt of calcium, since in all other cases the
latter is the more beneficial.1 Sodium sulphate is likewise of very
little neutralizing value, and the soluble salts of magnesium possess
none so far as was ascertained. Calcium sulphate raises the limit
only six times, the presence or absence of an excess of calcium ear-
bonate not affecting the value of the sulphate. This comparatively
slight efficacy of calcium sulphate in neutralizing ‘‘ black alkali” is
rather surprising in view of the accepted ideas of students of alkali
soils in regard to the curative value of gypsum.* The comparative
inefficacy of calcium sulphate in this case contrasts strikingly with
its power to neutralize sodium in the forms of sulphate (Table VII)
and chloride (Table VIII).

Calcium chloride is the only salt found to be very effective in
neutralizing sodium carbonate, raising the limit of enduranee for the
latter fifty times. A mixture of solutions of the two salts causes an
immediate heavy precipitate of calcium carbonate, to which fact the
efficacy of the added salt must be largely ascribed. We should be
dealing in this case with a solution of sodium chloride containing a
large excess of calcium carbonate. Yet by direct addition of solid
calcium carbonate to a solution of sodium chloride, the limit of endur-
ance for the latter can be raised only three times, i. e., to 0.06 normal
(see Table VIII). Here again chemistry appears to be powerless to
afford an explanation of a phenomenon which, in the present state
of our knowledge, must be regarded as paradoxical.®

A very noteworthy result was obtained by experiments with sodium
earbonate, as well as with sodium bicarbonate, in the presence of an
excess of calcium sulphate and calcium carbonate. In solutions of
critical concentration of both of these mixtures a majority of the
roots of the lupine plants were completely destroyed with pronounced

'The probability of the formation of a double carbonate, with a consequent
lowering of the active mass, as well as a probable change of nature of the ions,
suggests itself very forcibly in this connection. It is hoped that time and oppor-
tunity will be found in the near future to test this supposition in the laboratory.

? Hilgard, Bul. 128, Agr. Exp. Sta., Univ. Calif., pp.16 to 18 (1900). It should be
stated, however, that Hilgard recommends the application of gypsum under phys-
ical conditions which would not probably be considered analogous to those under
which the experiments here described were performed.

3In marked contrast with this anomalous case is that of the mixture of magne-
sium sulphate and calcium chloride, in which a precipitate of calcium sulphate is
formed and which is therefore to be regarded as a solution of magnesium chloride
containing a solid excess of calcium sulphate. Here the limit of endurance is the
same as when solid: calcium sulphate is added directly to a solution of magnesium
chloride. The same thing is true of a mixture of sodium sulphate and calcium
chloride in which the limit of endurance is the same as for sodium chloride plus
calcium sulphate,

ne Tn eee ot ee

{eae

=

ed

30

corrosion due presumably to the action of hydroxyl ions, while a
smaller number survived in apparently perfect condition, and this
occurred in repeated experiments. In critical solutions of other salts
and mixtures of salts; however, there was rarely such sharp differ-
ence in appearance between roots which survived and those which
died during twenty-four hours’ culture; as a rule none of the roots
were in normal condition at the end of the experiment. In other
words, the difference of individual plants in their power to resist toxic
action appears to be more pronounced in the case of the two carbonates
of sodium than of other ‘‘alkali salts.” This would indicate that the
selection of plants for resistance to ‘‘black alkali” offers a simpler
problem than where resistance to other components of alkali soils is
to be sought.

SODIUM SULPHATE IN MIXTURES.

Experiments with sodium sulphate in mixtures with other salts
show the following results:

TABLE VII.—Limits for sodium sulphate in mixtures.

Greatest endurable : : :
concentration of | Concentration of the

sodium sulphate. | salts added.

Name of salt added. In frac-

Hons Gra In parts | In fractions! In partsper
norris (wee 100,000 | of anormal | 100,000 of
Aolation: ofsolution.| solution. solution.
SRC ye ee Ot en Seas Oe ei ee ce 0. 0075 58 | | secscs cals ss.) eo
SP MIMNICMORICG..2—. = 2-22.22 oh se wap eee eee . 00375 26.5 0.01 58
MatletannGllOrigde, s-8 se 2 Se eee Spee acne -2 1,272 .2 1,102
Maenesinm Carbonate... -55:22582-5,.-552. - 54555 . 03 212 Saturated. Saturated.
leriin CacCWOUAaLGis =. 62. 225 ee ore ee es 04 281 Saturated. Saturated.
PCI: SULDUALC S5-- 255-2 ce nen oe ee sa ae .5 3, 530 Saturated. Saturated.
Calcium sulphate and calcium carbonate a -.-- 3 1, 908 Saturated. Saturated.

aSee Bul. 17., p. 22 et seq., Division of Soils, U. S. Department of Agriculture, 1901.

Sodium sulphate is very abundant in ‘‘alkali” soils, often occurring
in contact with each or several of the other salts. In the Billings,
Mont., type, for example, it is accompanied by the sulphates of mag-
nesium and calcium, while in the Fresno, Cal., type it is in contact with
sodium carbonate.

Most effective for neutralizing this salt is calcium sulphate, which
raises the limit more than sixty times when added alone. In the
presence of an excess of calcium carbonate, however, calcium sul-
phate can increase the limit of endurance for sodium sulphate only
about forty times. This is probably due to a foreing back of the dis-
sociation and decrease of solubility of the calcium sulphate by the
calcium carbonate, although, as Cameron and Seidell! have shown,
either salt is rather soluble in dilute solutions of sodium sulphate.

‘Solution Studies of Salts Occurring in Alkali Soils, Bul. 18, Division of Soils,
U.S. Department of Agriculture.

36

As in the case of all the other salts except sodium carbonate, eal
cium chloride is less effective than calcium sulphate, raising the limit
only twenty-seven times. In this case, as in the mixture of calcium
chloride with magnesium sulphate, a crystalline precipitate of caleium
sulphate is formed, so that it actually becomes a ease of the contact
of calcium sulphate with a solution of sodium chloride, and the same
limit was obtained by a direct test of this latter mixture. Calcium
carbonate is much less effective in neutralizing sodium sulphate than
in counteracting the toxic action of magnesium salts.

Calcium sulphate is more effective as an antidote to sodium sulphate
than to any other salt tried except magnesium sulphate. In both
these cases the anion of the added salt is the same as that of the more

toxic one; hence the cathions alone seem to operate. Possibly a dou-

ble salt of sodium and calcium is formed in this mixture. Since eal-
cium sulphate is much less efficacious in neutralizing the chlorides of
magnesium and sodium than the corresponding sulphates, while it is
generally more beneficial than is calcium chloride, it seems almost
certain that the beneficial action of Ca ions is in some way hindered
by the presence of Clions. That Cl ions are in themselves less toxie
than are SO, ions would appear from the fact that the chlorides of
magnesium and of sodium are less injurious in pure solution than are
' the corresponding sulphates.

SODIUM CHLORIDE IN MIXTURES.

Experiments with sodium chloride in mixtures with other salts
yielded the results shown in the following table:

TaBLE VIII.—Limits for sodium chloride in mixtures.

Greatest endurable | ‘ .
concentration of Concer E ane oe the
sodium chloride. :

Name of salt added.

Hie ee In parts | In fractions | In parts per

= Sal | per 100,000} of anormal 160,000 of

Ralaniicae ofsolution.| solution. | solution.
MUO Oya aoe le Sachets wee ecl nc eae eee eee 0. 02 THGE Sas SRE ee eee Se cae 2
Waleimmi Chloride a2 2 13 He oe oe eo ee ee 2 1,160. 0.2 | 1,101
Marnesium carbonates _.-_. .- 2-2 2.-222- --S-2-- . 04 232 | Saturated. | Saturated.
@alcimmicarbonate.. 2-655 eee eee . 06 348 Saturated. Saturated.
Calcium sulphate.-...--...- Lae nseeoeeae 2 1,160 Saturated. | Saturated.
Calcium sulphate and calcium carbonate --.--- .2 1,160 | Saturated. | Saturated.

Sodium chloride is probably the most widely distributed and gen-
erally abundant of the soluble components of alkali soils, occurring
practically wherever the land is notably impregnated with these
noxious salts.' As the above table shows, calcium sulphate and eal-
cium chloride are equally effective in neutralizing the toxicity of
soditm chloride, although in the case of sodium sulphate and the

1A notable exception is the Billings area in Montana.

37

soluble salts of magnesium, the former is decidedly more beneficial
than the latter.

As in the case of magnesium chloride, the presence of calcium
carbonate does not affect the neutralizing value of calcium sulphate,
although decidedly diminishing it in the case of magnesium sulphate ~
and sodium sulphate. It has been shown by Cameron and Seidell!
that an excess of solid calcium carbonate has but a very slight effect
on the solubility of caleium sulphate in sodium chloride solutions at
the concentrations here involved. And from the general resemblance
between the phenomena presented by calcium sulphate in contact
with sodium chloride and magnesium chloride solutions, it is proba-
ble that caleium carbonate would have alike effect in the latter cases.
It is to be regretted that laboratory investigations of the solubility of
solid caleium carbonate and caleium sulphate in contact with solu-
tions of soluble sulphates have not yet been made.

CALCIUM CHLORIDE IN MIXTURES.

In the experiments with caleium chloride in mixtures with other
salts the following results were obtained:

TABLE [X.—Limits for calcium chloride in mixtures.

| Greatest endurable | :
F Concentration of the
concentration of salts added

ealecium chloride.

Name of salt added. eee
ions) Of at In parts |Infractions| In parts
1 | Per i00,000| of anormal | per 100,000

culation, of solution., solution. | of solution.
AST ya Sep e eh ee oa 2 EE Pinon! 2 eae AMR 0. 25 TS i bee ee oc
Maenesium ‘carbonate. .2.-.2--222 2225-5 <-22 ee 25 1,377 | Saturated. | Saturated.
mucum- carbonate: 22-2. : 24. Pt a0 1,377 | Saturated. Saturated.
walcium sulphate 8) 2 cae ee ee bela Base a0.3 1,652 | Saturated. | Saturated.
a About.

Calcium chloride is quite generally distributed in alkali soils, being
usually present in small patches wherever sodium chloride is abun-
dant. As would be expected from the relatively very high conecentra-
tion of the pure solution of this salt endured by roots of the white
lupine, the limit can not be materially raised by the addition of other

salts.
SODIUM BICARBONATE IN MIXTURES,

Sodium bicarbonate was tested in mixture only with calcium sul-
phate and calcium carbonate together, which raised its limit of endur-
ance two and one-half times (see Table X). It usually occurs in
nature in contact with the normal sodium carbonate.

CALCIUM SULPHATE AND CALCIUM CARBONATE IN MIXTURES.

In the tables of limits of endurance in mixtures, as in those of pure
solutions, the figures do not perfectly state the case. For example,

' Bul, 18, Division of Soils, U.S. Department of Agriculture (1901).

38

although the limit of endurance in sodium carbonate plus magnesium
carbonate is 0.01 normal, while for sodium sulphate plus magnesium
carbonate it is 0.03 normal, the proportion of individual seedlings
whose roots survive in good condition is decidedly greater in the latter
mixture than in the former.
None of the readily soluble salts occurs abundantly in alkali soils
save in the presence of calcium sulphate or calcium carbonate, and
most often in contact with both. Hence it follows that the limits of
endurance for the more soluble salts in the presence of these two salts
of calcium, as obtained by means of water-culture experiments,
should agree closely with the limits determined by soil investigators.
This proved to be the case, due allowance being made for the influ-
ence of the physical properties of a soil as compared with an aqueous
solution.
. The following table serves to bring together, for ready comparison,
the limit of endurance for roots of both white lupine and alfalfa in
solutions of six of the easily soluble salts to which a solid excess of
both calcium sulphate and calcium carbonate was added, the mixtures
being brought to equilibrium before using.

TABLE X.—Results with mixtures containing two caleium salts.

Limits for lupine | Limits for alfalfa
(Lupinus albus). | (Medicago sativa).a
Name of salt. eee | a
arts per arts per
100,000 of | WOFmal .|/n09, corer 4) Cuma
solution. | 5° ution. solution. | °° Biton:
Maenesigm Sulphate. -.a2-966 oe) =. eaten maa yee 2, 240 0.4 1, 960 0.35
Masresiuim: chloride: 5-205... 25... --s e 960 Be 960 3%
Sodium carbonaper ws tac. s esos We Sy eae, eee 156 . 03 104 . 02
Sodiumiusulphatens 2205) 2a hes aki Bee es 2,160 x 2,160 .3
modwumvenlonide:..Ses = s52 5 acne 2 aasce Se tate ee 1,160 2 1,160 .2
Sodimmypicarvoonwter oo: oo-ses-. 2 eee eee 417 05 667 . 08

alin the case of alfalfa a few roots barely survive in 0.°5 and in 0.38 normal magnesium sulphate,
while in 0.25 normal they make a noteworthy amount of growth during forty-eight hours. In
0.2 normal sodium sulphate they make a decidedly better growth, and in 0.1 normal sodium
chloride two and one-half times as much growth as in the water control.

The close correspondence between the white lupine and alfalfa in
their resistance to the effects of these mixed solutions is worthy of
note, especially as alfalfa appears to be more sensitive than the lupine
to pure solutions. The only serious discrepaney occurs in the mix-
ture of sodium bicarbonate, calcium sulphate, and calcium earbonate,
to which alfalfa roots appear to be nearly twice as resistant as are
those of white lupine.

That in the neutralizing effeet upon more toxie salts which these
two relatively insoluble salts exert calcium sulphate plays a much
more important part than does caleium carbonate is obvious from a
comparison of the limits of endurance in solutions to which either
calcium sulphate or calcium carbonate alone has been added. Indeed,
in the case of magnesium sulphate and of sodium sulphate the limit
of endurance is decidedly lower in the presence of both calcium salts

ae. ee
» |

ERR. I Dil Oe IT

ers rrr T Fake Aistiaies Deh bel

ae

39

than when calcium sulphate alone is added. On the other hand, the
presence or absence of calcium carbonate appears to have no effect
upon the neutralizing value of calcium sulphate when added to mag-
nesium chloride, sodium chloride, or sodium carbonate.

An interesting comparison is that of the soluble salts, one with
another, in respect to their degree of toxicity in pure solution on the
one hand, and in the presence of an excess of calcium sulphate and
ealeium carbonate on the other. It will be observed that the sequence
in the first column is very different from that in the second. The
most toxie salt or mixture is placed at the head of each column.

TABLE XI.—Order of toxicity with and without calcium salts.’

In pure solution: In presence of an excess of CaSO, and CaCO3;: a
Magnesium sulphate. Sodium carbonate.
Magnesium chloride. Sodium bicarbonate.
Sodium carbonate. Magnesium chloride.d
Sodium sulphate. Sodium chloride b
Sodium chloride. Calcium chloride.
Sodium bicarbonate. Sodium sulphate.
Calcium chloride. Magnesium sulphate.

alt has already been suggested that the limit in some of these highly concentrated solutions
containing an excess of calcium salts may bear some relation to the osmotic pressure of the
solution. It is therefore not a mere coincidence, perhaps, that the sequenze in this column is
almost identical with that in Table II (of concentrations precluding any growth during the
culture).

b These two salts are equally toxic in mixtures if reacting weights be compared, while magne-
sium chloride is the more toxic of the two in parts of salt per 100,000 of solution.

The interest and importance of the results obtained from the exper-
iments made with mixed solutions show the great desirability of
extending further this line of investigation. In fact, no aspect of the -
work promises more substantial returns. An interesting problem
among the many which suggest themselves in this connection is that
of a possible relation between the degree of toxicity of a salt, alone or
in mixture, and the readiness with which it is taken up by the plant
from a solution. The occasion seems opportune to redirect attention

to a series of experiments made long ago by Wilhelm Wolf? as to the

1'Landw. Versuchsst., 7, 193 (1865). The studies were made with a series of
solutions, each of which contained two salts in equal amount. Combinations
were made with (1) salts of the same acid, but of different bases; (2) salts of
the same base, but of different acids; (3) with both base and acid different. In
each culture 200 c. c. of solution was employed, and after one-half of this volume
had been absorbed by the plant (allowance being made for the small quantity of
water evaporated directly from the solution) the amount of each salt taken up
with the water was estimated by analysis of the residual 100 c. c. of solution.
Young beans and maize were used in the experiments. Some of the results
obtained were as follows:

From three mixtures, each containing 0.05 grams of each two salts, the plants
absorbed in percentages of the original quantity of each salt supplied:

From ammonium nitrate plus calcium nitrate, 92 per cent of the former and 94
per cent of the. latter.

From ammonium nitrate plus magnesium nitrate, 92 per cent of the former and
86 per cent of the latter.

From magnesium nitrate plus calcium nitrate, 74 per cent of each.

Potassium nitrate was taken up from all combinations with other nitrates

40

amount of each salt absorbed by a plant from a mixed solution.
Especially interesting, as compared with the toxicological phenomena
of pure and mixed solutions, respectively, are Wolf’s results as to
the effect of calcium sulphate in stimulating the absorption of other
sulphates.

GENERAL SIGNIFICANCE OF RESULTS WITH MIXED SOLUTIONS.

To enter into a discussion, from the purely chemical point of view,
of the widely accepted hypothesis of the dissociation of electrolytes
in solution would be to exceed the proper limits of this paper.' It
is sufficient to say that salts such as those with which we are here
dealing are held to dissociate in- dilute solutions, more or less com-

(Na, NH,, Mg, Ca) in absolutely greater amount than from a simple solution.
From a solution containing 0.025 gram each of potassium nitrate and calcium
nitrate the plants absorbed 100 per cent of the former and 88 per cent of the latter.
From an equivalent solution of potassium nitrate plus magnesium nitrate, 100 per
cent of the former and 88 per cent of the latter. The stimulation of the plant by
the presence of calcium to take up greater quantities of potash is referred by
Loew (l. c., p. 44) to the increased development of root hairs induced by the calcium.
But if the presence of magnesium has exactly the same effect, as would appear
from the experiment just quoted, we must look further for anexplanation. Absorp-
tion of ammonium nitrate is decreased by the presence of other nitrates, while
that of calcium and of magnesium nitrates is stimulated thereby. It is remarkable
that while neither of these last two salts is readily absorbed from a simple solution,
both are easily absorbed when mixed together.

Plants could be grown in mixtures of potassium and calcium sulphate
(K,SO, + CaSO,) and of calcium and magnesium sulphate (CaSO, + MgSO,), but
never in mixtures of sulphates of potassium and sodium (K,SO, + Na,SO,), of
potassium and ammonium (K,SO,-+ (NH,), SO,), nor of potassium and magnesium
K,SO, + MgSO,), even when the solutions were very dilute.

Potassium and ammonium salts were taken up much more readily in the pres-
ence of a calcium salt than from a pure solution. This was notably the case with
the sulphates, which are absorbed with difficulty from unmixed solutions. Gypsum
(calcium sulphate) is absorbed in very small quantity in the presence of a potas-
sium salt, but greatly stimulates absorption of the latter. From a mixture of
calcium and magnesium sulphate little of either salt is taken up, but the presence
of magnesium nitrate considerably increases the amount of calcium sulphate
drawn from a solution.

From mixtures of a sulphate and a phosphate, the latter is always taken up in
greater quantity. Maznesium sulphate is taken up in greater quantity in the
presence of a phosphate than are other sulphates.

De Saussure’s principle of the absorption of salts in solution by plant roots—
i. e., that the salt is taken up in smaller proportion to the water absorbed than it
occurs in the culture solution; in other words, that the residual solution becomes
more concentrated—applies to the absorption of sodium chloride in the. presence
of a nitrate (KNO,, NH,NO,, Ca(NO,).), but does not hold as to the absorption
of the nitrate itself.

1For the presentation of the subject in simple terms the reader is referred to
a former publication by one of us. (Rep. No. 64, U. S. Department of Agricul-
ture, p. 144, 1900.)

41

pletely at a given concentration according to the specific properties of
the particular salt. The result is a liberation of ions—atoms or atomic
groups carrying or in some way associated with an electric charge.
Cathions, those furnished by the basic radicle, carry positive elec-
tricity, while anions, derived from the acid radicle of the salt, are
negatively charged. Ions possess a much greater velocity * than do
undissociated molecules, and it is now believed by many physiologists
that salts owe to the properties of their ions rather than to their entire
molecules the toxic and other action which they exert upon organisms.?

It is believed that the results of the present investigation tend to
confirm this view, although it must be admitted that serious anomalies
exist, to some of which attention has already been directed. —

Pure solutions of the salts dealt with are shown to be generally
injurious to plants, and this largely by virtue of the cathions which
they yield, asa comparison of the position of the several salts in the
table of toxicity in pure solutions shows conclusively. Thus magne-
sium salts, irrespective of the character of their anions, are much
more injurious than is any sodium salt, while the three chlorides (of
magnesium, sodium, and calcium) differ enormously in toxicity,
regardless of the fact that they yield a common anion.

An inspection of the tables of limits in mixed solution given above
makes it clear that the addition of a second, less toxic salt in most
cases inereases the concentration of solution of the more harmful one
in which root tips can retain their vitality. It is also demonstrated
that addition of a second sali of the same base, hence furnishing a
different kind of anion only, is usually much less efficacious in raising
the limit than is the admixture of a salt of a different base. Thus
magnesium chloride is ineffective as an antidote to magnesium sul-
phate, sodium chloride to sodium carbonate or to sodium sulphate,
and calcium carbonate to calcium chloride.

If the assumption be granted that in the dilutions here involved
the magnesium salts are practically completely dissociated and that
the anions do not have a toxic effect, then a 0.00125 normal solution
of magnesium will be the limit when the metal is combined as the sul-
phate and a 0.0025 normal solution when combined as the chloride, but
about a 0.002 normal solution when both chloride and sulphate are pres-.
ent, with two equivalents of the former to one of the latter. The same
line of reasoning holds for the other cases cited, and from these facts it
is evident that the anions have a part in determining the toxic effect of a

'That the physiological action of ions may be in some scrt a function of their
specific velocities is indicated by Loeb’s comparison of the effects of hydrogen and
hydroxyl ions, as well as of various basic cathions, upon the absorption of water
by amuscie. [Pfliiger’s Archiv.. 69, 21, (1898).]

Of a rapidly growing literature on this subject the papers of Kahlenberg and
True and of Kahlenberg and Austin, dealing with plants, and those of Loeb,
Garrey. Anne Moore, Kahlenberg, Clark and others, treating ion action upon ani-
mals, may be cited as of great importance. (See the Bibliography, p. 56.)

49

salt, although a much smaller one in general than have the ecathions.
Furthermore, these views are in harmony with Loeb’s idea that SO,
ions are more toxic than Cl ions, because they tend to precipitate
calcium from its proteid compounds.

In other cases, however, addition of a salt which furnishes new
anions, but not new cathions, to the mixture is effective in raising the
endurable limit of concentration for the more toxic salt. A striking
case is the elevation of the limit for magnesium sulphate eight times
by the addition of magnesium carbonate. Here it would appear that
the HCO, anions alone ean be the effective agency. Sodium sulphate
slightly raises the limit of sodium carbonate, and a relatively unim-
portant increase of the-concentration of a calcium chloride solution
in which lupine roots can survive is obtained by addition of calcium
sulphate. But in these last two cases the effect is so small as to be
almost negligible, and is perhaps entirely attributable to the foreing
back of the dissociation of the more toxic salt rather than to any
direct physiological action of the new anions.

The superior efficacy of cathions over anions in neutralizing the
toxie effect of other cathions is illustrated by the discovery that
sodium is equally effective as an antidote to magnesium chloride,
whether it be added as sulphate (Na,SO,) or as chloride (NaCl).' A
much more striking illustration is afforded by the fact that calcium,
when added to a solution of magnesium sulphate or of sodium sul-
phate, is very much more efficacious when furnished as the relatively
insoluble sulphate than as the readily soluble chloride. In other
words, the presence of chlorine anions actually hinders the full exer-
tion of the physiological effect of calcium cathions, unless we are to
believe that the superior efficacy of calcium sulphate is due merely to
its greater influence in retarding the dissociation of the sulphates of
magnesium and of sodium.

If we turn now to the effect of mixtures in which two kinds of
cathions are present we find that these are almost invariably much
less poisonous than isthe pure solution of the more toxic salt. Even
the addition of a sodium salt (sulphate or chloride) to one of magne-
sium (sulphate or chloride) raises the limit of endurance for the latter
three to six times. Still more remarkable is the effect of magnesium
carbonate as an antidote to salts of sodium (carbonate, sulphate,
chloride), raising their limits two tofour times. but these effects are
trivial as compared with the extraordinary efficacy of calcium in
counteracting the toxie effects of other bases (magnesium, sodium).

Even when added as the but slightly soluble carbonate, calcium
raises the limit of magnesium sulphate and of magnesium chloride
sixteen times, of sodium sulphate more than five times, and of sodium

'On the other hand, sodium chloride is twice as SESE as sodium sulphate in
neutralizing magnesium sulphate.

'=—S + -—. ". i Tr

43

chloride three times. Calcium chloride’ mixed with an equal volume
of a magnesium or a sodium salt raises the limit of the latter as fol-
lows: Magnesium sulphate, one hundred and sixty times; magnesium
chloride, forty times; sodium carbonate, fifty times;* sodium sulphate,
twenty-seven times, and sodium chloride, ten times.

The most effective of the calcium salts tried was, however, calcium
sulphate. This, when added alone in solid excess, increases the
maxima of concentration endurable by the roots as follows: Magne-
sium sulphate, four hundred and eighty times; magnesium chloride,
eighty times; sodium carbonate, six times; sodium sulphate, sixty-six
times, and sodium chloride, ten times. Here we have probably the
greatest effect of one kind of ion in neutralizing the effect of another
kind that has yet been obtained in experiments with plants.

It is noteworthy that the effect of the calcium ions upon different
salts having a common basic ion differs greatly. Thus plant roots
can endure three times the concentration of a solution containing
magnesium cathions and sulph-anions to which calcium sulphate is
added than they can of a solution containing magnesium cathions and
chlor-anions plus calcium sulphate. Yet the former solution in the
absence of calcium salts is endurable in concentration only one-half as
great as is the latter without a calcium salt. Here the effect may be
partly due to differences of dissociation in the two solutions. But it
appears necessary to attribute the greater part of it to an adverse
influence, presumably exerted by chlorine ions, upon the physiological
action of calcium ions inthe presence of magnesium ions. Similar
problems are suggested by the wide differences in the degree to which
ealcium sulphate can neutralize the toxic action of each of the three
sodium salts.

That the phenomena exhibited by the roots of plants in their reac-
tion to these various mixed salt solutions are not to be regarded as
mere functions of chemical changes in the solution itself is patent.
The problem is undoubtedly a much more intricate one, involving
chemical reactions of great complexity in the protoplasm of the plant
itself. In this connection it is important to call attention to the
strikingly similar results obtained by Loeb? as to the relative toxie
effect upon animals of pure and of mixed solutions.

A pure salt solution, e. g., of sodium chloride, was found to be

' Loew (Bul. No. 18, Div. Veg. Phys. and Path., U.S. Department of Agriculture,
p. 33), referring to an experiment made by Boehm, appears to doubt the value of
calcium in the form of the chloride as a plant nutrient, owing to the formation
of hydrochloric acid in the assimilation of calcium by the plant. Here is another
suggestion as to the reason for the inferiority of calcium chloride to calcium sul-
phate in neutralizing the toxic action of salts of other bases.

? As has already been noted (under Table VI), a heavy precipitate of calcium
carbonate is formed in this mixture. so that it becomes in great part a solution
of sodium chloride plus a solid excess of calcium carbonate.

*See the papers by this author cited in the Bibliography (p. 58).

44

strongly poisonous to marine animals in various stages of develop-
ment—i. e., a fish (Mundulus heteroclitus), a jellyfish (Gonionemus sp.),
and a sea urchin (Arbacia sp.). But the addition in small quantity
of a salt yielding another kind of cathion, such as magnesium, potas-
sium, and calcium, more or less neutralized this toxic effect, although
each of these salts was itself toxic in pure solution. As in the ease of
plants, caleium was particularly effective. That it is the cathions
rather than the anions added to the solution which are chiefly effective
as counter agents is evident from the fact that of each base the chloride
only was used. Moreover, in only one mixture of three chlorides
could fertilized eggs of the sea urchin be brought to an advanced
stage of development, but sodium bromide could be successfully sub-
stituted for sodium chloride in the mixture.! It is clear, therefore,
that the anions play a very subordinate part in the physiological
action of such mixtures.

Loeb suggests that the physiological effect of a pure solution,
whether toxic or stimulating, is attributable to a reaction whereby
various cathions which are assumed to enter into combination with
the proteids of the organism are replaced by the cathion of the sur-
rounding solution, in accordance with the law of mass. Thus, in
case of an animal or organ immersed in a solution of sodium chloride,
ions of calcium and of potassium would be forced from their organic
compounds and sodium ions would be substituted for them. This
would cause a disturbance of equilibrium and finally a cessation of
irritability in the tissues. Such effect can be prevented, or, if it has
not proceeded to the point of disorganization, counteracted by the
addition to the solution of salts containing the corresponding cathions,
i. e., potassium and calcium. Hence the author derives his concep-
tion of a ‘‘ physiologically balanced salt solution,” examples of which
are sea water, the blood of animals, and a mixture of definite concen-
trations of the chlorides of potassium, sodium, and calcium. The
chief function of such a solution is regarded as the maintenance of
‘‘a certain physical condition, a certain labile equilibrium, of the
protoplasm or the colloids.” ” 3

From considerations such as these, and from the discovery that a
close analogy as to absorption of water exists between the behavior of
a frog’s gastrocnemius immersed in a solution of a potassium, sodium,
or calcium salt and that of potassium, sodium, and calcium soaps,?
the development of Loeb’s theory of the existence and function of
‘‘ion-proteid compounds” was logically inevitable. The hypothesis
is stated as follows: ‘‘ Salts or electrolytes in general do not exist in
living tissues as such exelusively, but are partly in combination with

1 Amer. Journ. Physiology, 3, 442 (1900).
> Ibid., 3, 445 (1900).
3 See Pfliiger’s Archiv, 75, 303 (1899).

45

proteids. The salt or electrolyte molecules do not enter into this
combination as a whole, but through their ions. The great impor-
tance of these ion-proteid compounds lies in the fact that by the
substitution of one ion for another the physical properties of the pro-
teid compounds change. We thus possess in these ion-proteid com-
pounds essential constituents of living matter which can be modified
at desire, and hence enable us to vary and control the life phenomena
themselves. * * * If it be true that life phenomena depend upon
the presence of a number of various metal proteids (Na, Ca, K, and
Mg) in definite proportions, it follows that solutions which contain
only one class of metal ions must act as a poison. The reason for
this is that the one class of metal ions will gradually take the place
of the other metal ions in the ion-proteids of the tissues. Even a
pure NaCl solution must thus be poisonous, although this salt perme-
ates all our tissues and is the main constituent of the [soluble] inor-
ganic matter of the ocean.”!

Pauli,” who published the same hypothesis almost simultaneously,
states his views with greater positiveness. ‘‘ The general distribu-
tion of the ion-proteid compound in the living organism can not be
doubted; indeed, we have strong reasons for the assumption that all
the proteids of the protoplasm exist there only in combination with
ions.” And again, ‘*‘ Not salts, but salt-ions, are indispensable to the
organism.” ®

Loeb’s experiments show that to the same ions or mixtures of ions
different animals or different organs or stages of development of the
same animal may react in a different manner. This was noted in the
case of embryonic as compared with fully developed tissue and with
myogenic as compared with nuerogenic contractions. Thus in pure
solution magnesium chloride is more favorable to the development of
fertilized eggs of the sea urchin than is sodium chloride, although the
latter causes while the former prevents rhythmical muscular contrac-
tion. On the other hand, as the predominant salt in a triple mixture
of chlorides (potassium and calcium being present in much smaller
quantity), sodium chloride favors, while magnesium chloride pre-
vents, the development of fertilized sea-urchin eggs.‘ Calcium ions
prevent rhythmical muscular contraction, but allow the muscle to
retain its irritability much longer than is possible in a solution trom

1 Amer. Journ. Physiology, 3, 327 (1900).

> Ueber physikalisch-chemische Methode und Probleme in der Medizin, 19,
Wien (1900).

$Loew, although attempting no such extensive generalization, has touched upon
the question of ion proteids and their relation to vital phenomena in his discus-
sion of the harmfulness to plants exhibited by magnesium salts in the absence of
calcium. (See Bul. No. 18, Div. Veg. Phys. and Path., U. S. Department of
Agriculture, p. 42, 1899. )

4Amer. Journ. Physiology, 3, 489 (1900).

46

which they are absent.’ Results similar to those obtained by Loeb
have recently been recorded by other investigators.’

That the converse case may also occur is indicated. by Loeb’s inves-
tigations: ‘* Different combinations of ions may exist which all have
the same effect. It seems as if the physical condition of the colloids
were the essential point and that this might be affected by various
ion combinations in the same way.” ?

It is not to be doubted that many peculiarities in relation to ions
will likewise be discovered in plants as compared with animals. A
case in point is that of magnesium chloride, which in pure solution is
eight times as toxic as sodium chloride to roots of the white lupine
and of alfalfa while the two salts are about equally toxie when eal-
cium is present. Hence lupine roots react toward these two salts in a
wholly different manner than do sea-urechin eggs. Furthermore, a
comparison of different plants, one with another, or of different organs
or stages of development in the same plant, will surely reveal numer-
ous dissimilarities.

The importance of the ion-proteid theory as an aid to the study of
the effects, both toxic and beneficial, which solutions of electrolytes
induée in organisms, can hardly be overestimated. It is to be regarded
as the only really scientific explanation of this class of phenomena
which has yet been attempted. Incomplete as the theory is in its
present form, and many as are the anomalies needing further study,
we can not but welcome it as a most promising instrument wherewith
to attack the vast problem of the physical properties and energies of
protoplasm.‘

Meanwhile it is highly desirable that te study of ion action upon
plants be extended. Experiments should be made with a larger num-
ber of different ions, and with mixtures containing more than two
kinds of cathions.° It is most essential that many species of plants
be tested in order that we may determine what classes of reaction to
ions are peculiar to certain groups of organisms and what, if any, may~

1 Festschrift fir Adolf Fick, p. 111 (1599).

*See the papers of Garrey, Anne Moore, Cushing, Lillie, and Stiles cited in the
Bibliography, (p. 56). True has lately experimented with Cladophora gracilis
grown in various synthetic solutions resembling sea water, and has made the
highly interesting discovery that an indefinite prolongation of life could be
obtained only when a solution equivalent to sea water in its other components,
but containing much more NaCl, was employed. Addition of calcium and potas-
sium salts was found necessary in order to neutralize effectively the toxic action
of a sodium salt solution.

3’ Amer. Journ. Physiology, 3, 443 (1900).

4For certain limitations of the theory as now formulated reference should be
made to the very important paper of Kahlenberg |Journ. Physical Chem., 5, 339
(1901) ].

> Loeb’s discovery that fertilized eges of the sea urchin could be developed to the
pluteus stage in mixtures of three, but not of two chlorides, indicates that much
is to be expected from such an extension of these investigations. See Amer.
Journ. Physiology, 3, 441, (1900).

. re [eee

f
;
‘
7
,
:
,

be regarded as generic properties of protoplasm. No less important,
as Loeb’s work with animals has conclusively shown, will be the com-
parative study of different organs and functions and stages of growth
in the same plant, as to their different reactions to the same ions and
combinations of ions.

From the point of view of agriculture the ion-proteid theory will
doubtless throw light upon much that is now obscure and even para-
doxieal in the relation between the plant and the soluble components
of the soil. Nothing is more certain, in the light of such observations
as are recorded in this paper, than the inadequacy of soil physics and
soil chemistry alone to explain many details of this relation. The
chemistry of protoplasm and its proteid compounds must surely be
taken into account before we may hope to get to the bottom of the
subject.

STIMULATING EFFECT OF DILUTE SOLUTIONS.

As an incident of these investigations it was demonstrated that in
the case of certain salts, when plant roots are exposed to pure solu-
tions which are much too dilute to produce any toxic effect, there
occurred a decidedly stimulating effect upon growth, as compared
with that in the distilled-water control during a corresponding period.
As would be expected, this was shown to be the case for salts of eal-
cium, both the chloride and the sulphate acting as stimuli. Here,
however, we have to do with salts which contain valuable elements
of plant food.

But a marked stimulating action occurs in pure solutions of sodium
carbonate (slight in 0.002 normal, marked in 0.00125 normal and of
sodium bicarbonate 0.01 normal). The most pronounced effect was
obtained in a 0.00125 normal solution of sodium carbonate, the average
elongation of the roots in that solution being one and one-half times
as great as in distilled water during the same period. In the case of
the two carbonates of sodium it seems necessary to regard the effect as
one of chemical stimulus, pure and simple. That this is not due to the
sodium ions-is evident from the fact that very dilute solutions of other
sodium salts (sulphate, chloride) gave purely negative results. It was
at first thought that the physiological effects of sodium carbonate
(Na,CO,) were attributable to the presence of hydroxylions in the solu-
tion, since the corrosive, clearing action of more concentrated solutions
of this salt is precisely similar to that produced by potassium hydrate
and sodium hydrate. But toxic, as well as stimulating reactions of
exactly the same character were obtained with solutions of the bicar-
bonate (NaHCO,), in which a large excess of carbon dioxide was dis-
solved, and which gave no reaction with pheno!phthaleine, even at the
end of the experiment.' In this case the consideration of free hydroxyl

‘Solutions of sodium carbonate which were many times too dilute to produce a
stimulating effect, yet gave a stroug reaction with phenolphthaleine.

48

ions must be excluded. Hence the conclusion seems unavoidable that
the carbonic acid (HCO,) ions produce the stimulating effect, improb-
able as this would appear. ‘To what agency should be ascribed the
characteristic toxic action (so different in kind from that of sodium
sulphate and sodium chloride) of stronger solutions of sodium bicar-
bonate, in which no free hydroxyl could be detected, is a question to
which no answer can at present be given.!

None of the other salts with which experiments were made in pure
solution were shown to stimulate elongation of the roots, although
the possibility is not excluded that solutions still more dilute than
those employed will give positive results. Magnesium sulphate was
found to be indifferent (neither toxic nor stimulating) at 0.0003125
normal, magnesium chloride at 0.000625 normal, sodium sulphate
(nearly) at 0.002 normal, and sodium chloride? (approximant. ps at
0.005 normal.

These observations accord with the well-known principle that many
violent poisons, if given in sufficiently minute doses, serve as benefi-
cial stimuli. Familiar examples are the action of arsenic, mercury,

1In experiments with sodium carbonate and sodium bicarbonate as to their
effect upon animals, Loeb encountered a very similar anomaly. The stimulating
effect of various hydrates upon the absorption of water by a muscle immersed in
a sodium chloride solution was shown to-be clearly due to the hydroxyl] ions,
being equal in amount when equivalent solutions of hydrates were used, irre-
spective of the character of the basic ions [see Pfliger’s Archiv, 69, 10 (1898) ].
The similar effect produced by carbonates of sodium and potassium was ascribed
to the same factor, the hydroxyl] ions (l.c.,p.20). On the other hand, the effect of
sodium carbonate (Na,CO,) in stimulating skeleton formation in the pluteus of a
sea urchin appears to be due to the carbonic acid (HCO,) ions, since sodium in
other forms, as well as hydroxyl] in the form of potassium hydrate, gave negative
results [Am.Journ. Physiology, 4438, (1900) ].

° Pfeffer [Pflanzenphysiologie, Ed. 2, 1, 425] observes that possibly chlorides (e. g.,
sodium chloride), like so many other substances, act in dilute solutions as chem-
icalstimuli. Storp [Biedermann’s Centralbl., 13, 76 (1884) ] obtained a stimulating
effect upon the germination of seeds by immersing them in a 0.01 per cent solution
of sodium chloride. Jarius [Landw. Versuchsst., 32, 149 (1886)] found that
even a 0.4 per cent solution of sodium chloride stimulated the germination of seeds
of wheat, rye, rape, maize, beans,and vetches. Jones and Orton (Bul. Vermont
Agric. Exp. Station No. 56, p. 12) observed, as a consequence of the application of
sodium chloride toland in order to exterminate the weed known as Orange Hawk-
weed (i ieracium aurantiacum),a marked stimulating effect upon the growth of
grass in the same field. Peligot [Comptes rendus, 73, 1078 (1871)] suggests that
the stimulating effect upon field crops which is sometimes obtained with sodium
chloride may be due to its facilitating the decomposition of calcium phosphate
and thus increasing the amount of phosphoric acid at the disposal of the plant.
Kellner [Landw. Versuchsst., 32, 365 (1886)] attributes to a similar liberation of *
phosphoric acid the stimulating effects of iron sulphate upon plant growth recorded
by Koenig and by Griffiths (see p. 49). Réveil [De l’action des poisons sur les
plantes, p. 41 (1865) ] found that sodium hypochlorite in a solution of 0.1 per cent
stimulates germination and growth, but is injurious, especially to herbaceous
plants, when applied in greater concentration. :

49

strychnine, digitaline, etc., upon animals. Numerous investigators
have obtained similar effects with plants by supplying them with very
small quantities of various substances which can not be regarded as
sources of plant food, such as the extremely toxic salts of some of the.
heavy metals. In practically all such cases, however, it is very prob-
able that considerable hydrolysis had taken place and that the stimu-
lation might well be attributed to the hydroxyl ions thus introduced
into the solution.

Raulin experimented extensively with the fungus Aspergillus as to
the effect of various metallic salts in stimulating or hindering its
growth, his being among the first considerable work in this line.?

The well-known observations of Frank and Kriger? indicate that
copper in small quantities (furnished by spraying with Bordeaux mix-
ture) stimulates the growth of the potato, acting favorably upon almost
every organ and function, although this metal is well known to be

1 Ann. Sci. Nat., sér. 5, 11, 243 (1869).—The sulphates of zinc and of iron were
found to produce marked stimulating effect, the former increasing the dry weight
of the fungus two to three or even seven times, the latter about twice. In order
to show that the acid radicle was not responsible for the results. a corresponding
amount (0.06 gram of salt per 1,000 grams of culture solution) of ammonium sul-
phate was tried, but no stimulation was obtained. To demonstrate still more com-
pletely that basic radicles are here chiefly concerned other salts (nitrates of iron
and of zinc, zinc acetate, iron citrate) were tried and yielded stimulative effects
similar to those of sulphates. In cases where both iron and zinc were added to
the same culture solution (e. g., zinc nitrate plus ferric citrate, or ferric sulphate
plus zine acetate, or zinc acetate plus ferric citrate) the stimulating effect was
decidedly more marked than when only one base was used. When sulphates of
both zinc and iron were present the effect was nearly twice as great as in the
absence of the former, and was exactly twice as great as in the absence of the lat-
ter. The diminution of the stimulating effect was almost as great if instead of
merely withdrawing one or the other base an equal portion of the second base was
substituted for the first; in other words, when two parts of zinc (or of iron) were
substituted for one part each of zinc and of iron. The stimulating effect of the
different salts of zinc expresses itself in a crop from two to four and six-tenths
times. that of iron in a crop one and four-tenths to two and seven-tenths times as
great as in the pure culture solution.

Manganese was found to produce effects similar to those of iron and of zinc, but
**less constant, less appreciable.” Silica (as silicates of potassium and of sodium)
when added to the culture solution increased the dry weight of Aspergillus in the
ratio of 1.2 or 1.4 to 1.

Raulin wrongly concluded that zinc and silica are indispensable to this fungus,
but justly emphasizes ‘‘ this influence of infinitely small quantities of substances
upon vegetation ” (1. c., p. 253).

J. Koenig [Landw. Jahrb., 12, 837 (1883)] and Griffiths [Journ. Chem. Soc.,
1884, p. 71, and 1885, p. 46] obtained evidence of a stimulating effect of iron
sulphate upon the growth of p:ants by watering soils used in culture experiments
with a solution of this salt. On the other hand Kellner [Landw. Versuchsst.,
32, 365 (1886) |. following the same method of experiment, obtained only negative
results. . |

*Ber. d. deutsch. bot. Gesellsch., 12, 8 (1894),

8287—No. 71—02——-4

50

extraordinarily poisonous to plants.!| Miani? records the interesting
observation that in a vapor-saturated chamber the mere presence of
copper in the neighborhood of but not in contact with a hanging drop
of water containing spores of Ustilago and pollen grains of various
plants stimulated the germination of the latter. H. Schulz® found
that aleoholic fermentation is accelerated by the presence of a small
quantity of mercuric chloride and of other substances. The devel-
opment of Aspergillus and of Penicillium in glycerol cultures was
stimulated, according to Pfeffer,’ by the presence of small quantities
of zinc, manganese, cobalt, etc. Subsequently numerous experiments
as to chemical stimulation were made by Richards upon fungi.°

'For a classical discussion of the toxic effect of exceedingly dilute solutions of
metallic salts upon the alga Spirogyra, see Nageli, Neue Denkschr. schweizerischen
Gesellsch. f. gesammt. Naturw., 33 (1893). Copper in a solution of 1 part to
1,000,000,000 of water was found to be fatal! (l.c.,p.28.) Attention has lately
been redirected to the extreme toxicity of copper by Dehérain et Demoussy
[Comptes rendus, 132, 523 (1901) ] and by H. Devaux (1. c., p. 717). The latter’s
observation that protoplasm absorbs less copper when exposed during several
hours to a large quantity of a running very dilute solution (e. g., of 1 part copper
to 400,000,000 parts water) than when placed for a short time in a single drop of a
much more concentrated solution (1 part copper to 30,000 parts water) leaves wholly
unexplained the negative results as to the extraordinary toxicity of this substance
recorded by Miani [Ber. deutsch. bot. Gesellsch., 19, 461 (1901)], who immersed
his subjects for a long period in a single drop of solution. Niageli’s experiments
have been more recently repeated (upon Spirogyra and other organisms) by Israel
und Kiingmann [Virchow’s Archiv, 147, 293 (1897)], who made careful studies of
the ‘‘oligodynamic ” effects produced by extremely dilute solutions of copper. A
noteworthy contribution to this subject by Galeotti has lately appeared [Biol.
Centralbl., 21, 321 (1901)], in which the effect produced by a ‘‘ colloidal” solution
of copper [prepared after the electrical method recently described by Bredig and |
Miller in Zeitschr. fir physik. Chemie, 31, 258 (1899) ] is compared with that of an
‘‘ionic’”’ solution of copper sulphate containing an equivalent amount of copper.
This author found that the former (colloidal) solution piasmolyzed the protoplasm
of Spirogyra in a dilution (1 gram-atom copper in 12,600,000 to 126,000,000 liters of
water) at which the ionic solution (of copper sulphate) produced no effect what-
ever. He therefore concludes that the action of the colloidal solution is a catalytic
one, closely analogous to the catalyzing action of such colloidal solutions (of cop-
per and other metals) upon hydrogen superoxide.

> Ber. deutsch. bot. Gesellsch., 19, 461 (1901). ;

’Pfliger’s Archiv f. die gesammte Physiol., 42, 517 (1888).

+ Jahrb. fiir wiss. Botanik, 28, 238 (1895).

>Tbid., 30, 665 (1897). Richards experimented with sulphate of iron and with
salts of zinc, cobalt, nickel, and manganese, as well as other substances, using as
subjects one species each of Aspergillus, Botrytis, and Penicillium. Theestimation
of the amount of stimulus obtained was based upon the increase in dry weight of
the whole mass of mycelium in the culture as compared with that in a control free
from the stimulating substance. Zine sulphate was found to be the most power-
ful stimulant, while important results were also obtained with sulphates of iron,
cobalt, and nickel. Saltsof lithium were likewise very effective. It was found,
however, that acceleration of the development of the mycelium was accompanied
by an unfavorable influence upon the production of conidia, when salts of zinc or
of iron, amygdaline, or morphine were added to the culture solution. In »ther
words. a stimulation of one function or phase of development does not neces-
sarily imply stimulation of the organism as to all its functions,

ec 51

Recently an important paper upon the effect of certain chemical
stimuli upon fungi and alge has been published by Ono.!

Similar results as to the stimulation of life processes afforded by the
presence of small quantities of various non-nutritive substances have
been obtained in experiments with animals. Loeb? found this to be
true of certain acids, hydrates, and mineral salts, the accelerating
effect produced by the solutions upon the absorption of water by
muscles, the rhythmical contraction of muscles and the segmentation
of eggs being attributed to hydrogen ions, hydroxy] ions, or different
basic cathions, as the case may be.?

The as yet obscure problem of the mode of action of chemical
stimuli as regards plants has been discussed by Pfeffer,’ from whom
it may be permissible to quote at some length:

‘‘In the regulation of activity chemical stimuli certainly play a
very extensive part. It is obviously a matter of chemical stimula-
tion that the seeds of Orobanehe and of Lathrza germinate only
upon the roots of host plants, and probably the same occurs with
fungi. In the case of initiatory or only regulatory stimuli, there may
be partly involved substances which the organism does not neces-
sarily require. In fact, under certain circumstances very different
substances can cause an acceleration of activity. * * * These
and similar phenomena obviously arise from different causes. Partly
it may be a matter of physiological counter reactions, which can also,
for example, occasion an increase of respiration, of circulation of the
protoplasm, ete., in response to injurious or other action. In other
cases a more simple chemical acceleration of reaction may be con-
cerned, as in catalytic action.”

1 Journ. Coll. Sci. Univ. Tokyo, 13, 141 (1900). This author experimented with
various species of algze and fungi in order to determine their reaction to minute
quantities of the sulphates of zinc, nickel, iron, and cobalt as well as to sodium
fluoride, lithium nitrate, and potassium arsenate. He found a marked increase in
the total amount of vegetable matter produced in the presence of any one of these
substances, the increase in the case of algze being due, however, to the stimulation
of vegetative reproduction rather than to any marked increase in the size of indi-
vidual plants. The optimum dose for alge is considerably smaller than that
for fungi, 0.0001 gram molecule in most cases proving toxic to the former. Zinc
sulphate exerts the greatest stimulating effect. These salts (especially ZnSO,
and NaF1) tend to hinder the development of spores in fungi. Copper sulphate
and mercuric chloride stimulate the growth of fungi, but not of alge.

2 See all the papers of this author cited in the Bibliography.

3It is probably worth while at this point to call attention to the fact that in
nearly every case where this stimulative effect has been observed, electrolytes
have been used which are known to show marked hydrolysis, with the formation
either of hydroxyl ions, or more generally, as in the case of salts of the heavy
metals, of hydrogen ions. And it may well be that, as in the studies of Loeb, the
stimulating effects observed by former investigators may rightly be ascribed in
the majority of cases to the presence of these ions.

4 Jahrb. fir wiss. Botanik, 28, 238, 239 (1895).

52

In another work’ Pfeffer emphasizes the idea of counter reactions,
suggesting that ‘‘one has to do in this accelerating stimulation with
one of the manifold reactions which serve, through more intensive
activity, to counteract as far as possible an injurious influence or to

compensate injuries.” And again:? ‘‘Probably this [stimulating]
effect results from a general reaction of the organism against injurious
substances, since similar effects are induced by ether, alkaloids, ete.,
effects which also find expression in an increase of fermentation and
respiration. * * * Itiseasytounderstand * * * that further-
more such substances as are poisonous only in higher concentration
generally occasion no obvious [stimulating] effect.”

If it can be shown that such stimulating effect is sufficiently
permanent to express itself in a marked increase in the yield of a
crop, its economic importance would be obvious. That the pres-
ence of a certain amount of calcium salts in the soil may really act
as a chemical stimulant to growth, apart from the value of the salts
as plant food, or in rendering soluble other nutritive soil components
there appears to be some reason to believe. It is not impossible that
other substances, even perhaps those salts of magnesium and of sodium
which constitute the must noxious components of alkali soils, when
present in quantity too small to be harmful, may be actively stimula-
tive rather than merely indifferent to plants. That several of them
are likewise valuable as sources of nutritive material is well known.
Whether, after all, the distinction between the chemically stimulating
effect and the utility as food of certain mineral salts be always as sharp
as is commonly supposed, is a question which can not yet be regarded
as decisively answered.

ECONOMIC IMPORTANCE OF THE RESULTS.

Some of the facts ascertained by these experiments with salt solu-
tions in their effect upon plants have a direct practical bearing upon
agricultural conditions and methods in regions where alkali salts are
frequent. Attention is particularly directed to the effects obtained
by the addition of lime salts to others. Each of the common soluble
alkali salts is found to be very injurious when alone, but usually
much less harmful when two are mixed, especially when a salt of lime
is one component of the mixture. This is strikingly the case with sul-
phates of magnesium and of sodium, the noxious effects of these salts
being enormously lessened by the application of lime, particularly in
the form of gypsum or land plaster (the dihydrate of calcium sul-
phate). Contrary to the general impression, this corrective effect was
found in water-culture experiments to be considerably less for *‘ black
alkali” (sodium carbonate) than for any of the ‘‘ white alkali” salts,
although even the harmfulness of black alkali can certainly be greatly
diminished by the use of gypsum. .

1Pflanzenphysiologie (Zweite Auflage), 1, 374 (1897).
*Tbid., p. 409,

j 53

el A i i a lll

The soluble chloride of lime could apparently also be used to advan-
tage upon a soil which is strongly impregnated with alkali. With
this salt the best effects would be anticipated when it is used as a rem-
edy for black alkali, although it is likewise a powerful antidote for the
chloride and sulphate of soda and of magnesia. But, except in rare
instances, the use of chloride of lime upon a large scale is hardly prac-
ticable. The little-soluble carbonate of lime is likewise more or less
beneficial in all cases except that of black alkali, but it is a much
less powerful remedy than is land plaster (calcium sulphate).

Much economic value should attach to an extension of these experi-
ments by using mixtures of more than two salts. It would thus be
possible to imitate more closely the conditions which obtain in alkali
soils, where several or all of these salts usually occur together.
Furthermore, other kinds of plants should be tried in order to deter-
mine to what extent plants differ one from another in their power to
resist the effect of various combinations of alkali salts. In this con-
nection experiments should be made with wheat, barley, sugar beets,
and other important crops of the region, as it may be found that one
crop is better adapted than another to withstand the effects of this or
that type of alkali soil. |

This leads to the possibility of selecting alkali-resistant breeds of
each of the leading crops. By observation of a stand of wheat or of
alfalfa which has been injured by the ‘‘rise of alkali” or by the use of
alkaline irrigating water, it is usually possible to find here and there
individual plants which have succeeded in surviving the injurious
effects of the salts. Similar differences in the power of individuals
to resist the action of alkali salts was detected in the culture exper-
iments. By continued selection of the seed of such resistant individ-
uals, sowing it season after season in alkali soil, there is reason to
hope that in time a race could be developed and fixed which would
flourish in soils containing a greater amount of alkali than can be
endured by the ordinary agricultural varieties.’ It will likewise be
very interesting to determine whether a race bred to resist black alkali,
for example, will also prove to be proportionately resistant to white
alkali, or whether it will be possible and desirable to develop differ:
ent races to suit different types of alkalisoil. An observation already
cited (see p. 34) would indicate that the different power of resistance
possessed by individuals of the same species of plant is brought out

1Observations made by Roos, Rousseaux, and Dugast [Ann. de la Science Agron.,
sér. 2, 6ieme année, 2, 336 (1900) ] indicate such differences among the grapes culti-
vated in Algeria. It was found that of different varieties growing in the same
soil the fruit of some absorbed less sodium chloride from the soil than was taken
up by others. As the sale of wine containing too high a content of sodium
chloride is prohibited by law in France, the economic importance of this discovery
is obvious. Although the problem here involved is somewhat different from that
of the power of resistance to the poisonous effects of a salt upon the plant. it serves
to illustrate the general principle that different individuals or races show marked
dissimilarity in their behavior in the presence of a given soil component.

54

more sharply in the presence of the carbonates of soda than when
other ‘‘alkali” salts are concerned.

So great appears to be the promise of results to be obtained by breed-
ing alkali-resistant races of the more important field crops of the far
western United States, that the Department of Agriculture has already
undertaken work on this line. During the past season experiments
with this end in view were begun under the direction of Mr. Webber,
of the Plant-Breeding Laboratory, Division of Vegetable Physiology
and Pathology. It is hoped that they will demonstrate the practical
value of this method of approaching the problem.

SUMMARY.

As the result of these preliminary studies, the following facts ean
be regarded as established:

(1) Those readily soluble salts of magnesium and of sodium which
are characteristic components of alkali soils are exceedingly injurious
to plants when exposed to pure solutions of them of concentration
above a minimum which is specific for each.

(2) They are toxie in the following sequence, beginning with the
most harmful: Magnesium sulphate, magnesium chloride, sodium ear-
bonate, sodium sulphate, sodium chloride, and sodium bicarbonate.

(3) Calcium chloride in pure solution is ten times less injurious
than sodium chloride, and two hundred times less injurious than
magnesium sulphate, if chemically equivalent solutions are considered.

(4) Magnesium carbonate in a saturated solution is not markedly
injurious, while magnesium bicarbonate in saturated solution acts as
a strong poison. Calcium carbonate and calcium sulphate are posi-
‘tively stimulating in saturated solutions, while calcium bicarbonate
appears to be decidedly injurious.

(5) The toxie effect of the injurious salts is due very much more to
the influence of the cathions (derived from the basic radicle) than to
the anions (furnished by the acid radicle).

(6) By mixture of equal volumes of two readily soluble salts, or by
the addition of a solid excess of a relatively insoluble to a solution
of an easily soluble salt, the toxic effect of the more harmful compo-
nent can in a majority of cases be diminished, or the concentration of
the more toxic salt endurable by the roots of plants can be increased.

(7) This increase is much greater in cases where a different kind of
eathion is added to the solution than when a new anion only is
introduced.

(8) Addition of sodium ions to a solution containing magnesium
ions in most instances markedly weakens the toxic action of the latter.

(9) Addition of calcium ions to solutions containing either sodium
or magnesium ions nearly always counteracts to an extraordinary
degree the injurious effect of the sodium or magnesium ions, this
beneficial influence being usually much more marked when calcium
is furnished as the sulphate than when the chloride is added.

55

(10) The ameliorating effect of calcium sulphate is much more
marked when it is added to sulphates of magnesium and of sodium
than when it is mixed with the corresponding chloride. It raises the
concentration limit endurable by plant roots in magnesium sulphate
four hundred and eighty times, in sodium sulphate more than sixty
times.

(11) Even plasmolysis, although supposedly a reaction to purely
physieal stimuli, can apparently be completely prevented by altering
the chemical nature of a solution without materially diminishing its
osmotic pressure. At any rate, plasmolysis was not detected in cases
where a solid excess of calcium sulphate had been added to a 0.5 or
even 0.4 normal solution of magnesium sulphate, although a pure
solution of magnesium sulphate is very strongly plasmolyzing at
the concentrations named.

(12) Calcium chloride appears to be peculiarly effective in neutral-
izing the effect of sodium carbonate.

(13) The effect of one kind of ion in counteracting the physio-
logical action of another kind can not be entirely explained by a study
of the chemistry of the solution itself, but must in part be referred
to complicated changes in the protoplasm of the organisms. The
theory that ions furnished by the dissociation of electrolytes form
intimate combinations with the proteids of protoplasm, and that
their mutually antagonistic effect expresses itself in a replacement
of one kind of ion by another as a result of change in the composition
of the surrounding solution, would appear to afford the key to this
problem. .

(14) At a certain degree of dilution all of these salts become
indifferent (i. e., neither toxic nor stimulating) in their action upon
plant tissues. The maximum concentration of the indifferent solu-
tion is likewise specific for each salt.

(15) At a still greater dilution some of them, as the salts of calcium
and the two carbonates of sodium, produce a positively stimulating
effect upon the growth of roots.

(16) Individual plants show a marked dissimilarity in their power
of resistance to the toxic action of the alkali salts. Such individual
differences are strikingly accentuated in solutions of sodium earbon-
ate and of sodium bicarbonate of the maximum concentration which
will permit any of the roots to retain their vitality.

CONCLUSION.

Too great stress can not be laid upon the fact that the experiments
upon which the present report is based are merely preliminary.
Furthermore, they were designed primarily to afford a standard for
comparison of the salts involved. It is not to be expected—indeed, it
is assuredly not true—that in the soils containing these salts the con-
ditions are quite comparable to those maintained in the laboratory in
ithe course of these investigations. The physical nature of the soil,

\S well as the presence of various other soluble substances, renders it

56

certain that nowhere in the field will these salts be found to have
anything like the poisonous effect which they severally exert upon
the roots of plants immersed in water solutions. Nevertheless it is
only from such experiments, conducted under simplified conditions,
that we can draw conclusions as to the actual effect of the components
of alkali soils upon plant growth.

It is very desirable that this line of investigation be continued and
extended. Further combinations, perhaps of more than two salts,
should be tested; an attempt should be made to imitate as closely as
possible natural soil conditions; plants in different stages of growth
should be tried, for in irrigated regions it often happens that a stand-
ing crop is exposed to a varying soil content of soluble salts at differ-
ent periods of its development. -Finally, it is highly important that
the experiments be repeated with other plants of widely different
relationship and, as far as possible, of actual agricultural importance
in the region concerned. For while we may assume for the present
that the same sequence of harmfulness of the several salts will obtain
in the case of most or all ordinarily cultivated plants, this is open to
doubt, and it is quite certain that the actual limits of endurance differ
in the case of different plants.

BIBLIOGRAPHY.

ASKENASY, E.—Ueber einige Beziehungen zwischen Wachsthum und Temperatur.
Ber. deutsch. bot. Gesellsch., 8, 61 (1890).

BoODLANDER, G.—Ueber die Léslichkeit der Erdalkalikarbonate in Kohlensiiure-
haltigem Wasser. Zeit. fiir physik. Chem., 35, 25 (1900).

Brepia & MULLER.—Ueber anorganische Fermente. I. Ueber Platinkatalyse
und die chemische Dynamik des Wasserstoffssuperoxyd. Zeit. fiir physik.
Chem., 31, 258 (1899).

CAMERON, F. K.—Application of the theory of solution to the study of soils.
Report 64, U. S. Department of Agriculture, pp. 141 to 172 (1900).

CAMERON, F. K.—Soil solutions. Bulletin No. 17, Division of Soils, U. 8. Depart-
ment of Agricuiture (1901).

CAMERON, F. K.—Solubility of gypsum in aqueous solutions of sodium chloride.
Bulletin No. 18, Division of Soils, U. S. Department of Agriculture; Journ.
Physical Chem., 5, 556 (1901).

CAMERON & Briaes.—Equilibrium between carbonates and bicarbonates in
aqueous solution. Bulletin No. 18, Division of Soils, U.S. Department of
Agriculture (1901); Journ. Physical Chem., 5, 537 (1901).

CAMERON & SEIDELL.—Solubility of gypsum in aqueous solutions of certain elec-
trolytes; solubility of calcium carbonate in aqueous solutions of certain
electrolytes in equilibrium with atmospheric air. Bulletin No. 18, Division
of Soils, U. S. Department of Agriculture (1901).

Ciark, J. F.—Electrolytic dissociation and toxic effect. Journ. Physical Chem.,
8, 263 (1899).

CLARK, J. F.—On the Toxic Walne of Mercuric Chloride and its Double Salts.
Journ. Physical Chem., 5, 289 (1901).

Couptin, H.—Sur la toxicité du chlorure de sodium et de l’eau de mera | ‘égard des
végétaux. Rév. Gén. de Botanique, 10, 177 (1898).

Coupin, H.—Sur la toxicité des composés du sodium, du potassium et de l’ammo-
nium al’égard des végétaux supérieurs. Réy. Gén. ae Botanique, 12, 177/
(1900).

kd Me Me bi ee oe |

rh

Coupin, H.—Sur la résistance aux agents chimiques du protoplasma a l'état de
vie ralentie. Comptes rendus Soc. Biol., 53, 541 (1901).

Covpin, H.—Sur la sensibilité des végétaux supérieurs a des doses trés faibles de
substances toxiques. Comptes rendus Acad. Paris, 32, 645 (1901).

Coupin, H.—Sur !a sensibilité des végétaux supérieurs a l'action utile des sels de
potassium. Ibid., 1582.

CusHiInG, H.—Concerning the poisonous effect of pure sodium chloride solutions
upon the nerve-muscle preparation. Amer. Journ. Physiology, 6, 77 (1901).

Curtis, C. C.—Turgidity in mycelia. Bul. Torr. Bot. Club, 27, 1 (1900}.

DANDENO, J. B.—The application of normal solutions to biological problems.
Bot. Gazette, 32, 229 (1901).

DEHERAIN & DEMOUSSY.—Sur la germination dans l'eau distillé. Comptes rendus
Acad. Paris, 132, 523 (1901).

Devaux, H.—De ladsorption des poisons métalliques trés dilués par les cellules
végétales. Ibid., p. 717.

DrupveE, O.—Handbuch der Pflanzengeographie. Stuttgart (1890).

ENGEL, M. R.—Sur la dissolution du carbonate de magnésie par l ‘acide carbonique.
Comptes rendus Acad. Paris, 100, 444 (1885).

ENGEL, M. R.—Sur la formation de l*‘hydrocarbonate de magnésie. Ibid.,p. 911.

EscHENHAGEN.—Ueber den Einfluss von Lésungen verschiedener Concentration
auf das Wachsthum der Schimmelpilze. Stolp (1889).

FRANK und KRUGER.—Ueber den Reiz, welchen die Behandlung mit Kupfer auf
die Kartoffelpflanze hervorbringt. Ber. deutsch. bot. Gesellsch., 12, 8
(1894).

FREITAG, C. J. DE.—Ueber die Einwirkung concentrirter Kochsalzlésungen auf
das Leben von Bakterien. Archiv fiir Hygiene, 11, 60 (1890).

GALEoTTI, G.—Ueber die Wirkung kolloidaler und elektrolytisch dissoziirter
Metalll6sungen auf die Zellen. Biol. Centralbl., 21, 321 (1901).

GARREY, W. E.—The effects of ions upon the aggregation of flagellated infusoria.
Amer. Journ. Physiology, 3, 291 (1900).

GRIFFITHS, A. B.—Researches on the growth of plants under special conditions.

Chem. News, 47, 27 (1883).

GRIFFITHS, A, B.—Experimental investigations on the value of iron sulphate as
a manure for certain crops. Journ. Chem. Soc. London, 45, 71 (1884).
GRIFFITHS, A. B.—On the application of iron sulphate in agriculture and its

value asa plant food. Ibid. 47, 46 (1885).

HEALD, F. D.—On the toxic effect of dilute solutions of acids and salts upon plants.
Bot. Gazette, 22, 125, t. 7 (1896).

HILtGarpD, E. W.—Nature, value, and utilization of alkali lands. Bul. No. 128,
Agr. Exp. Sta. Univ. of California (1900).

ISRAEL & KLINGMANN.—Oligodynamische Erscheinuugen (v. Nigeli) an pflanz-
lichen und tierischen Zellen. Virchow’s Archiv, 147, 293 (1897).

Jarius, M.—Ueber die Einwirkung von Salzlésungen auf den Keimungsprocess
der Samen einiger einheimischen Culturgewaichse. Landw. Versuchsst.,
32, 149 (1886)

JENTYS, S.—Sur l’influence de la pression partiale de l’acide carbonique dans l’air
souterrain sur la végétation. Bul. Internat. Acad. Sci., Cracovie (1892), 306
(1893).

JONES & OrTON.—Orange Hawkweed or ‘‘ Paint Brush.” Bul. No. 56, Vermont
Agric. Exp. Sta. (1897).

KAHLENBERG, L.—The theory of electrolytic dissociation as viewed in the light
of facts recently ascertained. Journ. Physical Chem., 5, 339 (1901).
KAHLENBERG and AUsTIN.—Toxic action of acid sodium salts on Lupinus albus.

Journ. Physical Chem., 4, 553 (1900).

KAHLENBERG and MEHL.—Toxic action of electrolytes upon fishes. Journ.

Physical Chem., 5, 113 (1901).

58

KAHLENBERG and TRUE.—On the toxic action of dissolved salts and their electro-
lytic dissociation. Bot. Gazette, 22,81 (1896).

KELLNER, O.—Untersuchungen iiber die Wirkung des Eisenoxyduls auf die Vege-
tation. Landw. Versuchsst., 32, 365 (1886).

KLEMM, DS DesoneanieatioMecescnemimn ees der Zelle. Jahrb. fiir wiss. Botanik,
28, 627. tt.8,9 (1895).

Knox, W. F.—Ueber das Leitungsvermégen wasserigen Lisungen der Kohlen-
siure. Ann. Phys. Chem., 54, 44 (1895).

LILLIE, R.—On differences in the effects of various salt solutions on ciliary and
on muscular movements in Arenicola larve. Amer. Journ. Physiology, 5
56 (1901).

Lors, J.—Physiologische Untersachangon tuber Ionenwirkungen. Mitth. 1.
Pfliger’s Archiv fiir die gesammte Physiologie, 69, 1 (1898); Mitth. 2,1.c., 71,
457 (1898).

Logs, J.—Ueber die Aehnlichkeit der Flissigkeits-resorption in Muskeln und in
Seifen. Ibid., 75, 303 (1899).

LoeEps, J.—Ueber die Bedeutung der Ca- und K-Ionen fiir die Herzthatigkeit. Ibid.,
80, 229 (1900).

LorB, J.—Ueber Ionen welche rhythmische Zuckungen der Skelett-muskeln
hervorrufen. Festschrift fiir Adolf Fick 101, Braunschweig (1899).

Logs, J.—On the nature of the process of fertilization and the artificial produc-
tion of normal larve (plutei) from the unfertilized eggs of the sea urchin.
Amer. Journ. Physiology, 3, 135 (1899).

Loe, J.—On ion-proteid compounds and their rdle in the mechanics of life phe-
nomena. 1. The poisonous character of a pure NaCl solution. Ibid., 327
(1900). |

Logs, J.—On the different effect of ions upon myogenic and neurogenic rhythmi-
cal contractions and upon embryonic and muscular tissue. Ibid., 883 (1900).

Logs, J.—On the artificial production of normal larvae from the unfertilized eggs
of the sea-urchin (Arbacia), Ibid., 434 (1900).

Logs, J.—Further experiments on artificial parthenogenesis and the nature of the
process of fertilization. Ibid., 4, 178 (1900).

Loes, J.—Experiments on artificial parthenogenesis in annelids (Chetopterus)
and the nature of the process of fertilization. Ibid., 428 (1901).

Logs, J.—On an apparently new form of muscular irritability produced by solu-
tions of salts (preferably sodium salts) whose anions are liable to form
insoluble calcium compounds. Ibid., 5, 362 (1901).

LogEw, O.—The physiological rdle of mineral nutrients. Bul. No. 18, Div. Veg.
Phys. and Path., U.S. Dept. Agric. (1899).

LOPRIORE, G.—Ueber die Einwirkung der Kohlensaure auf das Protoplasma der
lebenden Pflanzenzelie. Jahr. fiir wiss. Botanik, 28, 531, tt. 6, 7 (1895).

Miani, D.—Ueber die Einwirkung von Kupfer auf das Wachsthum lebender
Pflanzenzellen. Ber. deutsch. bot. Gesellsch., 19, 461 (1901).

Moore, ANNE.—The poisonous action of saline solutions. Amer. Journ. Physi-
ology, 4, 386 (1900).

Moore, ANNE.—The effect of ions on the contraction of the lymph hearts of the
frog: ibid.,75, 87 Clis0r)-

NAGELI, C.—Ueber oligodynamische Erscheinungen in lebenden Zellen. Neue
Denkschr. d. schweizerischen Gesellsch. fiir die gesammten Naturwiss., 33,
51 pp. (1893).

Ono, N.—Ueber die Wachsthumsbeschleunigung einiger Algen und Pilze durch
chemische Reize. Journ. Coll. Sci. Imp. Uniy. Toky6, 13, 141, t. 13 (1900).

OvERTON, E.—Ueber die osmotischen Eigenschaften der lebenden Pflanzen- und
Tierzelle. Vierteljahrsschr. Naturf. Gesells ch. Ziirich 40, 1 (1895).

: | : 59

;

;

PavuLi, W.—Ueber physikalisch-chemische Methode und Probleme in der Medizin.
Wien (1900).

_ PeELiIcoT, E.—Sur la répartition de la potasse et de la soude dans les végétaux.

Comptes rendus Acad. Paris, 73, 1072 (1871).

PFEFFER, W.—Ueber Aufnahme von Anilinfarben in lebende Zellen. Unters.
aus der bot. Institut Tiibingen, 2, 179 (1886).

PFEFFER, W.—Ueber Election organischer Nihrstoffe. Jahrb. fiir wiss. Botanik,
28, 205 (1895).

PFEFFER, W.—Pfianzenphysiologie. Ein Handbuch der Lehre vom Stoffwechsel
und Kraftwechsel in der Pflanze. Zweite Auflage, erster Band (1897).
PFEIFFER, E.—Ueber die electrische Leitungsfihigkeit des kohlensauren Wassers

und eine Methode, Flissigkeitswiderstiinde unter héhen Drucken zu messen,
Ann. Phys. Chem., 23, 625 (1884).
Rav iy, J.—Etudes chimiques sur la végétation. Ann. des Sci. Nat., sér. 5, 11,
93 (1869).

=— REVEIL.—Recherches de physiologie végétale. De l’action des poisons sur les

plantes. Paris (1865). !
RicHarps, H. M.—Die Beeinflussung des Wachsthums einiger Pilze durch
chemische Reize. Jahrb. fiir wiss. Botanik, 30, 665 (1897).
RICHTER, A.—Ueber die Anpassung der Siisswasseralgen an Kochsalzliésungen.
Flora, 75, 4, tt. 1, 2 (1892).
Roos, RoussEAux et DuGAsT.—Rapport sur les vins des terrains salés de l’Algé-
rie. Ann. de la Sci. Agronom., sér. 2, 6iéme année, 2, 276 (1900).
Sacus, J.—Ueber den Einfluss der chemischen und physikalischen Beschaffenheit
des Bodens auf die Transspiration der Pflanzen. Landw. Versuchsst.,
1, 203: (1859); Gesammelte Abhandl., 1, 417 (1892).
Sacus, J.—Ueber das Wachsthum der Haupt- und Nebenwurzeln. Arbeiten des
bot. Instituts Wiirzburg 1, 385, 584 (1873-74); Gesammelte Abhandl., 2
773 (1893).
ScHIMPER, A. F, W.—Pflanzengeographie auf physiologischer Grundlage. Jena
(1898).
ScHLOESING, TH.—Sur la dissolution du carbonate de chaux par lacide car-
bonique. Comptes rendus Acad. Paris, 74, 1552 (1872)
ScHuLz, H.—Ueber Hefegifte. Pfliiger’s Archiv fiir die gesammte Physiologie,
42, 517 (1888).
SIGMUND, W.—Ueber die Einwirkung Chemischer Agertien auf die Keimung,
Landw. Versuchsst, 47, 1 (1896).
STANGE, B.—Beziehungen zwischen Substratconcentrationen, Turgor und Wachs-
thum bei einigen phanerogamen Pflanzen. Bot. Zeitung, 50, 253 (1892).
STEWART, JOHN.—Effect of alkali on seed germination. Ninth Ann. Rep. Utah
Agr. Exp. Sta. p. 26 (1898).
STILES, P.J.—On the rhythmic activity of the esophagus and the influence upon
it of various media. Amer. Journ. Physiology, 5, 338 (1901).
Store, KOniG u. a.—Ueber den Einfluss von Kochsalz-und Zinksulfathiltigem
Wasser auf Boden und Pflanzen. Biederm. Centralbl., 13, 76 (1884).
TREADWELL & REUTER.—Uber die Loslichkeit der Bikarbonate des Calciums und
Magnesiums, Zeitschr. fiir anorgan. Chemie, 17, 170 (1898).
TRUE, R. H.—On the influence of sudden changes of turgor and of temperature on
growth. Ann. of Botany, 9, 365 (1895).
TRUE, R. H.—The physiological action of certain plasmolyzing agents. Bot.
Gazette, 26, 407 (1898).

' An extensive bibliography of the earlier literature of the subject is given by
this author (pp. 169 to 176).

60

Truk, R.H.—The toxic action of a series of acids and of their sodium salts on
Lupinus albus. Amer. Journ.Sci., ser. 4, 9, 183 (1900).

Vries, H. pzE.—Eine Methode zur Analyze der Turgor. Jahrb. fiir wiss. Botanik,
14, 427 (1884).

WALKER & CORMACK.—Dissociation constants of very weak acids. Journ. Chem,
Soc. 77, 5 (1900).

WHITNEY & MEANS.—Alkali soils of the Yellowstone Valley. Bul.14, Div. Soils,

. U.S. Dept. Agric. (1898).

WoLF, W.—Die Saussure’chen Gesetze der ree von einfachen Salzl6-
sungen durch die Wurzeln der Pflanzen. Landw. Versuchsst., 6, 203 (1864. )

Wo.tr, W.—Chemische Untersuchungen tiber das Verhalten von Pflanzen in der
Aufnahme von Salzen aus Salzlésungen, welche zwei Salze gelést enthalten.
Ibid., 7, 193 (1865).

ae ae | CC

Te T ae

*

FORMATION OF SODIUM CARBONATE, OR BLACK ALKALI, BY
PLANTS. it,

By FRANK K. CAMERON,

INTRODUCTION.

Considerable attention has been paid within the past few years to
the possibility of growing valuable forage crops on some of the alkali
soils of the arid West. This subject was first taken up in California.!
The great value of saltbushes for certain soil conditions and for cer-
tain kinds of cattle feeding seems to be well established, but as both
Hilgard and Goss? have pointed out there is an element of danger,
expressed in the prevalent belief that most of these plants, including
the greasewood, chico, and other indigenous plants, convert the less
harmful neutral salts, such as sodium chloride and sodium sulphate,
into alkali carbonates—that is to say, the less harmful ‘‘ white alkali”
is converted into the more noxious ‘‘black alkali,” as has been
shown by the presence of sodium carbonate immediately under such
plants, whereas no trace of it exists some distance away. It may be
possible that the plants with their enormous root systems actually
gather up minute traces of sodium carbonate, which may be present
in lower depths of soil, gradually causing an accumulation at the
surface on the decay of their roots and branches. But the generally
accepted hypothesis of the conversion of the neutral salts appears
more probable, as will be seen in the course of this paper. It would
seem probable that plants growing in bunches or mats would be more
effective in producing these localized black-alkali spots, but some of
the most striking illustrations of this phenomenon have been observed
in connection with more upright species, such as Sarcobatus vermi-
culatus, the common ‘‘greasewood” of the West.

In the study of the alkali soils of the arid regions the field parties
of the Division of Soils have found the local flora of great value in
indicating the character of the particular soils where they are found.
This apparent relation between the plant and the salts present in the
soil became of interest in this connection and was referred to the

1 University of California, Agricultural Experiment Station, Bul. No. 125 (1899),
?New Mexico College of Agriculture and Mechanical Arts, Agricultural Experi-
ment Station, Bul. No. 22, p.41 (1897).

61

62

laboratory for consideration. The results of some preliminary inves-
tigations have proved of such interest as to warrant immediate
publication. |

CREOSOTE BUSH.

. Aspecimen of the creosote bush? ( Covillea tridentata) was examined.

This, while a desert plant, is said to shun soils where there is much
water-soluble salts. Mr. Means states that its presence can be taken
as a Sure indication of land free from injurious quantities of alkali.
It is found in dry, well-drained upland soils.

The material was thoroughly air dried. The leaves and stems were
then carefully separated, and both of the separated samples were
ground fine in an agate mortar. <A portion of each sample was burned
toash. The finely ground air-dried material and the ash were each
carefully leached with successive small portions of water until the
leachings ceased to show the presence of chlorides. The leachings in
each case were then brought together and made up to a volume of 500
cubic centimeters, and the various determinations were made with
100 cubic centimeter portions. The carbonates? were determined
by titrating with a twentieth normal (N/20) solution of hydrogen
potassium sulphate until loss of color, using phenolphthaleine as indi-
cator. So soon as the color had disappeared a drop or two of a solu-
tion of potassium chromate was added and the chlorine determined
by titrating with a tenth normal (N/10) solution of silver nitrate.
The sulphates, when determined, were estimated gravimetrically as
barium sulphate in the usualmanner. For convenience the acids thus
found to be present are stated as the corresponding sodium salts.
This procedure seemed to be justified by a subsequent determination
of the amount of sodium present in the solution. It is a well estab-
lished fact, and a fainiliar one to chemists, that when a salt of an
alkali metal is burned down with charcoal or other organic matter a
part of the mineral acid is volatilized and driven off, the alkali base
forming a carbonate, which is a stable compound even at quite high
temperatures. Nevertheless this is a point often overlooked in the
discussion of ash analyses. In obtaining the ashes the examinations
of which are described in this paper, very great care was exercised to
reduce the amount of this loss of the mineral acid as far as possible,
and the burning was done at as low'a temperature as possible. In
some cases the large amount of fused salt in the burning ash coated
the charred organic matter in such a way as to render further com-
bustion at a comparatively low temperature quite impossible. In these
eases the combustion was. stopped, the fused salts leached out with
water, and the residue reburned. It seems probable, as will appear
from the results which will be presented, that the loss of mineral acids

1Collected by Mr. Thos. H. Means near Tempe, Ariz.; kindly identified for us
by Mr. F. V. Coville.

*Report 64, Division of Soils, U. S. Dept. Agr. (1900); Amer. Chem. Jour., 23,
571 (1900). Bul.18, p.77, Division of Soils, U.S. Department of Agriculture (1901),

|

63

in the burning of the plant to ash was kept down to a very small per-
centage by following the procedure described.

The data obtained on examination of the ashes from the creosote
bush are presented in the following table:

TABLE XII.—Analysis of the ash of the creosote bush.

| Leaves
Leaves. andsmall| Stems.
| stems.
Mine hinalsampleorams <2. 225 8. 2s a 2k..- 22 Scb S55. e222 8. 5659 3. 6942 | 6. 6445
“SEEN AG RTS] PE SEIT 1S ele eee 7 eee a Sa ye ee eae eee . 8282 "3795 | . 3710
PS emeent Ob iiihGe = =. 522227 i ee We ees od a cate e ed | 9. 66 10. 27 5. 58
Na»,CQs, per cent of ash - EE BREE OE Ns pg NS 8. 90 13.18 17.73
NaCl, per cent of ash- -__.--- AREAS Nery) oe Peat re boil Toe 3.55
NaeCOs, per cent of air- -dried. plant __ So CLES ROT Se ein ae age . 86 1.35 .99
Mee ger ect of air-dried piant 20. oe i eee 55 | J55y lel: ee

The dry leaves, which had been ground fine in a mortar, were
extracted with distilled water at the room temperature in the manner
described above. The extract failed to show the presence of either
sodium carbonate or sodium chloride, but appeared to be slightly acid.
An extract made by boiling the leaves with water also failed to show
any chlorides or carbonates.

From the facts which have been presented it would appear that
while the plant does contain chlorine there is no sodium chloride
present as such, and therefore it is probable that the chlorine is in
organic combination although nothing is definitely known of the
presence of such combinations in plants. The sodium is largely in
excess of the amount required to balance the chlorine as sodium chlo-
ride. This fact was shown by an actual determination of the sodium.!
It would seem, therefore, that at least a large part of the sodium in the
plant is in organic combination, possibly with some organic acid, and,
on combustion or ultimate decay.of the plant tissues, much sodium
carbonate would be formed, as was found to be the case when the plant
was reduced to ash in the laboratory.

It is interesting to note that the mineral constituents, as shown by
the ash analyses, had accumulated in the leaves to about twice the
amount in which they were held by the stems. The difference is very
much less, however, if we consider only the water-soluble constitu-
ents in the ashes. Assuming, for the sake of argument, that the base
in combination with the carbonic acid and chlorine as determined was
entirely sodium, its distribution is shown by the following table:

TaBLE XIII.— Distribution of sodium in leaves and stems.

|
Percentages calculated for air-

Percentages calculated for ash. dried plant

Part of plant. ~~ =o ih —

From From From From Fr
| NaoCO;. | NaCl. Total. | Wa.CO; | NaCl. Total.
|
“oO Ti - 3.86 | 2.25 6.11 0.37 0.22 0.59
ES 6 re. 7.69 | 1.40 9.09 43 07 | - 150
i

‘Unfortunately it was not anticipated at the time this determination was made
that the exact figure would be required in this discussion, and the data were not
entered in the laboratory notebook and have been mislaid,

64

It appears that in the leaves there was about 2.7 times as much
sodium as was necessary to balance the chlorine, while in the stems
there was more than seven times as much of the base as the acid would
require. This suggests the possibility that the chlorine was being
eliminated through the leaves, probably in the form of some volatile
compound, which may be the source of the odor from the plant. This
idea is brought out somewhat more strikingly, perhaps, by noting that
the analytical figures given above indicate that the total amount of
water-soluble mineral constituents in the leaves is 1.19 times the
amount in the stems, but that the amount of chlorine in the leaves is
2.75 times that found in the stems; from which it would appear that the
chlorine was being concentrated in the leaves and, as has been pointed
out, was there present, in all probability, in organic combination. This
is a point which merits further attention, and it is hoped that it will
be the subject of a more thorough investigation in the future.

GREASEW OOD.

A more thorough examination of a specimen of greasewood !. (Sarco-
batus vermiculatus) was made. This is a typical ‘‘ alkali plant,” its
presence being usually regarded as a good indication of much water-
soluble material in the soil. Mr. Means reports that whenever he has
observed it the soil generally shows the presence of sodium carbonate,
the only exception being in Montana, where the soluble salts are
entirely sulphates. It would appear that this latter statement war-
rants further examination of the locality mentioned.

The analytical results obtained from examination of the ashes
follow:

TABLE XIV.—Analysis of the ash of the greasewood plant.

Leaves 1 Leaves

and blos- | and blos- | Stems.

soms (1). | soms (2).
NweIchtolisampleweraimis 2 sae i ess sabes eens ee ee eee ee 10. 6395 5.0000 | 10.6817
NWieteht of ash oramcre = aeee os) ot Ne 2 ae ee See eee ae a eee 2. 7505 1.17386 5274
NSH percent, Of pl aimte. shee ep ae See ee ee eta rk Stine, epee ene 25. 85 23.47 4. 94.
Nas CO peri centiObeash Gens. a= Seen ee eee aes tere Sian es ee 51.93 57.90 29.46
NaCl ipericent foftasine Aes ee eae ee a ee Bape 20. 47 22.24 - 14.31
Nao OF ET COM ile tas a ce cel ae eam ee Ne ae Pecan es See ar ae 5 3.69
NasCO2 percentioteair-driedyplant mes sees se se aeenee eee eee 13. 48 13. 69 1.45
Na @lepericent otgaiedrieguplantiecs ene eee eae eee 5.29 5. 22 sf
WeASOn, Sie Gay Git hip CheNeCl joey aye Soe ean es Sess tek: 230 Ge ice seater ate 1.18

1 Owing to the relatively large amount of fused salts which coated the carbon or other organic :
matter, this latter could not be completely burned off when reducing such a large sample to ash.

Five grams of leaves and blossoms, by successive leachings with
distilled water at room temperature until the leachings aggregated 2
liters, gave (1) 5.81 and (2) 5.68 per cent of sodium chloride. In both
experiments the washings showed no trace of soluble carbonates, but
were slightly acid. The residue from (1) after ignition gave a trace
of sodium chloride and 0.04 per cent of sodium carbonate.

‘Collected by Mr. Frank D, Gardner near Salt Lake, Utah.

“ce

ea Re

>

wr

65

By the method of Carius—that is, heating in sealed tubes with fum-
ing nitric acid and silver nitrate— |

(1) 0.2327 gram of leaves and blossoms gave 0.0310 gram AgCl,
equivalent to 5.43 per cent of sodium chloride.

(2) 1.0759 grams of leaves and blossoms gave 0.1432 gram AgCl,
equivalent to 5.43 per cent of sodium chloride.

From these results it would appear that the plant contains chlorine,
but, within the limits of experimental error, all the chlorine is present
as sodium chloride, which can be leached out with water at ordinary
temperatures. This is probably true of the major part of the sul-
phates also, although this was not shown quantitatively. <A striking
feature is the much larger amount of ash from the leaves and blossoms
than from the stems and the markedly larger percentage of the alkali

~saltsin the ash of the former. The idea suggests itself that possibly

this plant takes up and stores the salts and holds them as such
until it is ready to use such part of them as it needs.’ On the other
hand, it may be, for all that we now know, that these salts are
present as described only beeause the plants can not prevent their
accumulation, and, so far from being an inherent feature of the plant’s
economy, it may be a most undesirable accident due to their peculiar
environment, but an accident in spite of which these particular plants
are able to survive.* But, as Schimper? has pointed out, this can not
be true in all eases, as evidenced by the fact that halophilous plants
show a tendency to take up more salts than nonhalophilous species,
even when grown in nonsaline soils.

None of the chlorine, apparently, was in organic combination, this

‘Schimper [Indomalayische Strandflora, p. 12 (1891): Pflanzen-Geographie,

_ p. §9 (1898)]- has expressed the opinion that halophytes thrive on salty soils

because of a peculiar physiological structure which enables them to reduce to a
minimum the evaporation from their leaves and, in consequence, the absorption
of the salt solutions in the soil through their roots. The sait content of their sap
is thus kept below a certain concentration, although this concentration may,
and often does, greatly exceed that which would be determined by ‘‘ osmotic
equilibrium.”

Stahl [Bot. Zeitung, p. 139 (1894)] observes that only a fewspecies, such as
Reaumuria hirtella, described by Volkens [Die Flora der Aegyptisch-Arabischen
Wiiste, p. 27 (1887)], are known to be able to free themselves from the salt.

Diels [Jahrb. fiir wiss. Botanique, 32, 316 (1898) ] objects that Stahl experimented
with cultivated p‘ants and: that the retarded root action noted by Schimper does
not take place under natural conditions, and that, as a matter of fact, and probably
through the agency of malic acid, most, if not all, the halophytes rid themselves of
an excess of chloride. Diel’s methods of experiment, as well as the conclusions
which he draws from his own premises, are criticized by W. Beneke, Jahrb. fiir
wiss. Botanique 36, 179 (1901).

Directly bearing upon this hypothesis is an observation by Detmer [ Bot. Zeitung,
42, 791 (1884) ] that ‘‘ organic acids under the condition prevailing for the vegetable
organism are in a position-to decompose chlorides with a formation of free hydro- -

-chloric acid.” See also, Osborne, Report Conn. Ag. Ex. St., 1900, p. 441.

> Contejean, Geog. Bot., p. 71.
*Schimper, Pflanzengeographie, p. 101 (1898).

SO07= No- 71 oe

66

plant being in striking contrast in this respect to the Covillea tri-
dentata examined above.

Another interesting point is that the leachings of the air-dried
leaves and blossoms must have contained about three times as mueh
sodium as was necessary to balance the hydrochloric and sulphurie
acids present in the plant. The total amount of sodium calculated
from the ash analysis would be 8.32 per cent. A direct determination
of the sodium made on an aliquot part of the leachings gave 8.55 per
cent, while the amount calculated as necessary to balance the hydro-
chlorie and sulphuric acids, as determined by the ash analysis, is 2.68
per cent. The residue after leaching contained practically no echlo-
rine, sulphates, or carbonates. It would appear that in the burning
of the plant or in its deeay the sodium, which is probably present in
organic combination, yields sodium carbonate as a decomposition prod-
uct, and this in turn is found in the ash or débris. It seems probable
that a large part of the chlorine which was originally taken up or at
least held by the plant in the form of sodium chloride has been thrown
off by the plant in some manner, the sodium being retained in organic
combination.

ABSORPTION OF MINERAL CONSTITUENTS BY THE PLANT.

Inspection of the analyses of the ashes of plants in general, whether
leaves, stems, or in fact any part of the plant tissues, shows that there
are more than enough base-forming elements to counterbalance the
possible inorganic acids which the results indicate to be present.
Moreover, the ashes are alkaline. It is still an open question as to
how these bases, which appear in excess, or, more generally, how all
the bases, are taken up and assimilated by the plants and what
becomes of the acid radicals. While it is possible that some of the
alkaline materials may have been absorbed by the plant in the form
of carbonates as such, the amount thus absorbed will be relatively
very little, for by obvious metathetical reactions or double decom posi-
tions there would be formed carbonates of the alkaline metals. These
latter would be hydrolized in water to some extent, giving caustic
solutions which would undoubtedly corrode the tissues of the plants.

The question as to the disposition.of the acid residues is then perti-—

nent. Several possible explanations suggest themselves, which seem
worthy of attention in this connection.

It is possible that chlorine, for example, which may have been in
the acid radical, has been changed by the plant in such a way as
to form organic substances. and that these organic substances may
be exhaled by the plant as odors or exuded by the leaves or roots.
Against the latter suggestion the experiments of Diels! indicate that
the excretion of such substances by the roots is very improbable. On
the other hand, the chlorine or sulphur may be retained in the plant
tissues in organic combination in such form that they more or less

Jahrb. fiir wiss. Botanique, 32, 316 (1898).

|
|

ae

67

completely disappear on combustion, the organic combination volatil-
izing as such, or by devomposition yielding volatile products contain-
ing the chlorine or sulphur.t In evidence against this view are the
results obtained in the examination of the sample of Sarcobatus
vermiculatus, where it was found that the total amount of chlorine in
the plant, as determined by the Carius method, in which there was
afforded no opportunity for any of the chlorine to escape, was the
same as the amount leached out of the ashes by water, within the
limits of experimental error.

Another idea that presents itself is that the bases and acids are
taken up by the plant in the form of salt solutions; that the plant
selects and retains the bases and excretes the acid radicals in some
manner as acids. It is noteworthy, in this connection, that it has
been observed generally in the cases of water cultures that the nutri-

ent solutions gradually become acid unless special conditions are

introduced to prevent it. Occasionally, however, cases have been
found where the culture solutions actually become alkaline.” The
point of special importance in this connection is that either a base or
an acid radical, more often the latter, is either rejected or ejected by
the plant.

It seems to have been id patty supposed that the acidity of these.
solutions was due_to organic acids formed and excreted by the plant,
but no satisfactory proof for this view has been adduced. The weight
of evidence is now decidedly against this view. It is not at all diffi-
eult, from the point of view of the chemist, to construct a probable
‘“mechanism ” for the phenomena presented, supposing that the plant
has selectively retained the basic constituents and exereted the acids,
and that the acidity of the culture solutions is due to the free mineral
acids. Diels’s* investigations in this direction are particularly interest-
ing. He found that certain halophilous plants, when placed in distilled
water, steadily lost the sodium chloride they contained. He showed
that the salt was not excreted as such,‘ and offers as a probable expla-
nation that the greater amounts of malic acid—the forimation of which.
is shown to be a usual accompaniment of growth in succulent plants,
such as most of the halophytes are—decomposes the sodium chloride,
forming sodium malate and hydrochloric acid, and this latter is possi-
bly exereted by the roots.’ The solutions become acid, but, on account
of the oe nei difficulties, it was not definitely proved that the

Tt i is Be eed to imply that chlorine a Saree may not play very aifter
ent parts in the plant economy, but the general considerations advanced might
be true for either of these or other elements.

* Witness the classical investigations of Stohmann, Sachs, and Knop, described
by Johnson in How Crops Grow, p. 180.

*Loc. cit. See also Kearney, Contributions from U. 8. National Herbarium,
Vol. V, No. 5, p. 277 (1900); and Benecke, Jahrb. fiir. wiss. Botanique, 36, 179 (1901).

* This point was established as early as 1865 by Wolf, Landw. Versuchstt., 7 pp.
20, 211 (1865).

° See reference to Benecke on p. 64.

~.

68

acidity was due to the presence of hydrochloric acid. It is intended
that some experiments in this direction shall soon be made in the
laboratory.

A somewhat simpler explanation than the one just described may

be offered—simpler because it does not require that the plant must
first take up the acid radical and then go through the reverse process
of exuding it again. It is known with reasonable certainty that a
certain amount of hydrolysis takes place in aqueous salt solutions,
although the absolute amount may be, and with ordinary strong elee-
trolytes usually is, very small indeed; nevertheless, it does take
place to some extent, and it seems not impossible that the plants
might show their selective properties in the solution, taking up the
base more rapidly than the acid, the latter in consequence being left
in greater proportion in the culture or soil solution. Of classical
importance in this connection is the work of Kuhn,! who found that
when maize was grown in a solution containing ammonium chloride,
the ammonium residue was partly taken up by the plant and hydro-
chloric acid remained in the solution. In fact, there does not seem
to be any inherent difficulty in supposing that the plant might selec-
tively absorb any ion for which it might have a special predilection.
As soon as this ion is removed from the solution the corresponding
ion with its opposite charge of electricity must either be removed
from the solution by precipitation or volatilization, for example, or it
at onee reacts with the water. Supposing the ion removed by the
plant to be a base, the action of the remaining acid ion on the water
must necessarily be accompanied by the liberation of oxygen from
the water of the solution. Whether or not any observation of this
kind has been made I do not know, but the liberation of the oxygen
might very well take place so slowly as to eseape detection. The
question as to what becomes of the electrical energy on the ion which
the plant absorbs will be answered in a consideration of the work
energy, heat energy, or other equivalent forms of energy involved in
the mechanism of the absorption process, and does not necessarily
demand further consideration at this point.’

It must be admitted in all frankness that the known facts in our
possession are not sufficient to justify a positive opinion as to the
views just presented. They seem, however, to be founded on a
rational basis and are put forward tentatively as suggestive of possi-
ble lines of investigation and the justification for formulating them
here will be found in the results of future work. Whatever may be
the bearing of this work on the ideas here presented, it can not fail
to be of the utmost importance in throwing light upon the difficult
problem of plant nutrition.

1 Henneberg’s Journal, pp. 116 and 135 (1864).

> These views are not intended to imply that salts can not be taken up as such,
even by nonhalophilous plants, under certain conditions. Woif (loc. cit.) has
long since shown that this may be done, and that, moreover, in such cases the
process can not be a simple diffusion phenomenon.

‘so ee

69

From the data presented above it is evident that in the decay of
wood or leaves or, in general, of plant tissues, alkaline carbonates
are furnished to the soil. It may be that the processes of decay will
furnish at the same time organic acids stronger than carbonic acid
and in sufficient quantity to combine with all the bases and prevent
an alkaline reaction. As has been shown in this laboratory carboni¢
acid itself may be formed in sufficient amounts to convert all the
carbonates to the form of bicarbonates and thus prevent an alkaline
reaction. There is not sufficient evidence to justify a positive state-
ment, but it would seem probable that this can not be always the casé
and that in fact there is alkali formed by the decay of plant tissues.
In humid regions the alkali thus formed is removed by leaching or
similar processes and by chemical reactions with the other soil com-
ponents, for which reactions water is necessary.

In the arid regions, such as are found in the western part of the
United States, peculiar phenomena, due to the special conditions
there existing, have been observed. The indigenous plants which are
found on the alkali lands are comparatively few in number, both as
to species and as to individuals; others have been artificially intro-
duced. They all have the property of absorbing more or less large
amounts of water-soluble mineral salts and on analysis all show
characteristically large percentages of bases. When the leaves or
débris from these plants have decomposed there is often found greater
or less accumulation of carbonates, although before the plant was cul-
tivated that particular region may have been quite free from soluble
carbonates. The decay of any organic matter with the accompany-
ing formation of carbonic acid in a soil containing soluble salts of the
alkali metals must be expected to result in the formation of soluble
carbonates, partly by dissolving lime or magnesium compounds, fol-
lowed by subsequent metathetical reactions or double decompositions
with the alkali salts; more slowly and in lesser degree, perhaps, but
nevertheless surely, if the formation of carbon dioxide is continued,
by a distribution of the base between the two acids. This last proc-
ess, however, is probably of decidedly minor importance in the phe-
nomena under consideration.

Owing to the conditions of climate and drainage existing in the
arid regions these carbonates when formed are not leached away, as
in the humid regions, and gradually accumulate to the more serious
detriment of the soil.

COMPARISON OF ANALYSES.

For the purpose of comparison, two analyses of greasewood (Sarcoba-
tus vermiculatus) ash are here quoted, the first published by Hilgard,}
and the other by Goss and Griffin.’

1 University of California, Report of Agr. Exp. Sta., p. 142 (1890).

*New Mexico College of Agr. and Mech. Arts, Agr. Exp. Sta., Bu!. 22, p. 41
- (1897).

70

TABLE XV.—Two analyses of ash of greasewood plant.

; : First | Second
Constituents. analysis.| analysis.

Per cent.| Per cent.

imeAS IO falr-Grie diinlar hS ye oy ee te ee oe ed Seo i a aah oe eae ca 12.08 13.12

1 By difference. ~

While these analyses differ considerably in details they indicate the
same general conclusions; that is, the ash or decomposition products
of the plant will yield a very large amount of alkali in the form of
carbonates. The figures-in Hilgard’s analysis, he states, indicate the
presence of about 25 per cent of sodium chloride; about 8 per cent of
Glauber’s salt (Na,SO,10H2O), and about 39 per cent sodium carbon-
ate. Combining the figures of Goss and Griffin’s analysis in the con-
ventional way, we find about 13 per cent sodium chloride and 29 per
cent sodium carbonate. The figures are misleading, for they depend
upon an arbitrary calculation of the data as salts, and the effect of the
other constituents can not properly be ignored. Similarly, but a quali-
tative comparison can be made from the data obtained by us. If it
may be assumed that the leaves and stems are of equal mass in the
individual plants when air dried, our results compare quite well with
the analyses just cited.

Acknowledgments are due Messrs. F. D. Gardner and Atherton Sei-
dell for assistance in the experimental work described.

SUMMARY.

It would seem as a result of the experiments described in this paper
that in certain cases at least a transformation of neutral salts to the
corresponding carbonates through the agency of plant growth is pos-
sible and even probable, and that this factor must be taken under con-
sideration in determining the value and use of such plants. Some
tentative suggestions are offered as to the disposition of the mineral
salts in plant economy, which it is hoped will lead to more exhaustive
investigations.

RESISTANCE TO BLACK ALKALI BY CERTAIN PLANTS.
By FRANK K. CAMERON.

INTRODUCTION.

While working in the San Joaquin Valley, California, during this
past summer one of the field parties of the Division of Soils observed
three species of plants which appeared to be characteristic growths on
soils containing much ‘“‘ black alkali” or sodium carbonate. Super-
ficial examination in the field brought out the fact that the stems and
leaves of these three plants were quite acid, in some cases very
markedly so. <A possible connection was suggested between this fact
and the one first noted—that these plants were all found on soils con-
taining much sodium carbonate. Specimens were collected and sent
in to the laboratory for further examination. They were kindly
identified by Mr. Kearney, of the Division of Vegetable Physiology
and Pathology. They consisted of three samples of Distichlis spicata,
numbered I, II, and III; one sample of Suaeda intermedia, which was
separated into two portions, the first numbered IV, consisting of the
stems alone, and the second numbered V, being composed of leaves
alone; one sample of Atriplex bracteosa, which was also separated into
a portion numbered VI, consisting of stems alone, and a portion num-
bered VII, consisting of leaves alone.

Samples I, II, and III were thoroughly air dried by being allowed to
remain for about two months in the sacks in which they were received
at the laboratory. It should be stated that a rough determination of.
the acidity they displayed was made as soon as they were received in
the laboratory, and the results agreed fairly well with those vbtained
by the more careful examination subsequently made. |

Samples IV, V, VI, and VII were found to be very wet and in seri-
ous danger of fermenting when received at the laboratory. They were
therefore placed in a hot-air oven and dried for several days at from
105° to 110°C. In each ease the material was then cut into small
pieces and kept in carefully covered beakers, to which, however, the
air had free access.

METHOD OF EXAMINATION.

The method of examination was in all cases to steep the sample,
which had been cut into small pieces about a centimeter in length,
overnight or for about twenty hours in a convenient amount of dis-

71

12

tilled water.

About 600 eubic centimeters of the supernatant solution

was then decanted through a folded filter, and the analytical details
earried out with 100 cubie centimeter portions of the filtered liquid.
It was thought probable that this procedure would give a close approxi-
-mation to the soluble salts on the plant or held in its tissues in the

form of inorganic salts.

was evidently quite soluble in water.

The acid material on the surface of the plant
It was coneluded, as will be

shown later, that it was an organic acid, and that in all probability
considerable quantities of its sodium or other salts, as well as the acid
itself, were on the surface of the plant and dissolved in the water.
The amount of free acid was determined by titrating with a solution
of potassium hydroxide, which in turn had been earefully standard-
ized by titration against a twentieth normal (N/20) solution of acid
potassium sulphate. The other determinations were made in the con-

ventional way.

DISTICHLIS SPICATA.

TABLE XVI.—Distichlis spicata.

| Sample I. Sample IT. Sample III.
Grams of material - Ee eae | 13.12 30. 30 29.48
Cubic centimeters of leachings Zhe 750 1, 250 1,500
Percentage (mineral matter) leached
GoD er. ces ee Se LL eee aa 4,52 Dulle D. fe
Cubic centimeters N/20 acid equiva-
lent to lieram substances... -- sees | 23. 03 1.16 2. 48 -
Percent-| Per cent | Percent- | Per cent | Percent-| Per cent
age dis-| inair- | agedis-| inair- | age dis-| in air-
tribu- dried | tribu- dried tribu- dried
tion. |material.| tion. |material.| tion. |material.
| a e
Career fa Tae tS eS a 5. 62 0). 254 2.89 0. 148 3.25 0.186
Ee a CS FI a pe ee 1.86 . 084 Lae . 060 2.10 120
Nee ere Sos her eee See ae ee 41.30 1. 867 33. 12 | 1.696 27. 24 1.561
Kaen ree eed es Ne oe te SE De 13. 40 . 606 9.70 497 12. 23 . 701
SOc les UR per nese ss a eat ed a Sa ge 4,38 . 198 4.69 . 240 2.72 . 156
AS epee aN Ly et i ce ee ea 33. 44 1.511 48. 43 2. 480 52. 46 3. 006
100. 00 4.520 100. 00 5. 120 100. 00 5. 730
SO ee af pau ee Tae, ah oS A 6.19 280 6.64] .340 3.83 | — .219
Ca@loe es s25- SURO Spee Ne 10. 48 474 2.58 . 182 5. 90 . 338
INS CG SI TA rao Me ey ee ee 7. 25 828 4.57 . 234 8. 20 470
eed CT she So ii yen eas al ea em 25. 52 1. 154 18. 49 . 947 28.20 1.333
INIA CN Bis Mee ae aE TSR iia emer ear Se 15. 2% . 688 57.08 2. 922 52. 03 2.981
IN eee tee 2 ee heey een ae eae 35. 34 1.598 10. 64 545 6.77 . 388
100.00} 4.520] 100.00) 5.120| 100.00 5.780

TABLE XVII.—Soil (0-12 inches) in which Sample I of Distichlis spicata was found,

Per cent.)
ce Oa SENNGEE Cie Son Lip ep ie yaya oe em oN IE a) oe
(Sp ine NT ha SRC GM CO oR al GS F
IND Oee hose Ss abate: aa my aes ee Se | 33. 77
] Kea Ah ee ahaa RMR OE EO berg a NE Nal 1.81
BO sae eee co mR i ND ane ie LY Se eco 5. 44
, Ga AS eo ane passa anes MONET SLE oF 8.06
GO sre Bon Ae Son eh ee nan ee a 22. 63
HO Oso Sai SDA eae Sale 27. 65

~~ 100.00 |

wee een en en ee ee ene ree

| Percentage soluble, 1 gram soil to 20
cubic centimeters water --..--------

Per cent.

73

The analytical data obtained from an examination of the Distichlis
spicata—Samples I, IT, and I1]—are given in Table XVI. The most
striking point brought out is the very large amount of acid shown to
be on Sample I, amounting for 1 gram of the air-dried material to
the equivalent of 23 eubie centimeters of a twentieth normal (N/20)
acid. This substance was unquestionably an organic acid and a
fairly strong one. It did not appear to act on crystals of calcite very
readily. This might have been due, however, to the formation of a
slightly soluble lime salt, which would protect the calcite from the
solvent. The acid very readily decomposed the alkali carbonates and
neutralized not only ammonium hydrate but potassium or sodium
hydroxide in the presence of cochineal or phenolphthalein as indi-
cator. It will be seen by referring to the analytical figures that a
large amount of sodium is left after balancing the acids by the bases
found. This would seem to find its readiest explanation in supposing

that there was a much greater quantity of the organic acid on the
plant than indicated by the equivalent of 23 cubic centimeters of
) twentieth normal acid, but present in the form of the sodium or other

salts. By referring to the analysis (Table X VII) of the soil from which
this Sample I of Distichlis spicata was taken, it will- be seen that there
was relatively a very large amount of soluble carbonates present,
about 2 per cent of the soil being composed of these substances—an
amount which would absolutely prohibit the growth of any ordinary
plant, even though much of the salt was in the form of bicarbonate. |
Much of this material probably came in contact with the grass leaves,
in the form of dust or otherwise, with the result that the acid decom-
posed the carbonates with the formation_of salts of the organic acid.
These same views seem to hold for Samples II and III as well, but to
a lesser extent, as is shown by the quantitative measurements given.

It would appear from what could be learned in the field that this
grass, in the locality from which Samples II and III were taken, often
carries as much of the acid material as Sample I shows, or even more.
Unfortunately for this investigation the most favorable season for
securing samples had passed before Samples Il and III were gathered
and sentin. This subject will receive more careful attention during
another field season.

ISOLATION AND IDENTIFICATION OF ACID EXUDATION.

Careful attempts were made to isolate or at least to identify this
organic acid, but the attempts proved unavailing for several reasons.
But very little material was at command when the investigation was
taken up. The relatively large amounts of inorganic salts obtained
in the water extracts could not be well separated and presented great
analytical difficulties in the attempts to isolate so small a quantity of
the acid as was at our disposal. Attempts to crystallize the material
from solution, either as the acid itself or as a salt, proved -disastrous

74

on account of the rapid and abundant growth of fungi in the solution
when evaporation of the solvent at ordinary temperatures was
attempted. The solutions of the material failed to give any reactions
by which it could be identified as one of the simpler and better-known
organic acids. For these reasons efforts to identify it were abandoned

temporarily and further work on it postponed until a time when a

larger amount of the material could be obtained. It is confidently
believed that the experience thus far gained will insure a successful
issue to the next attempt in this direction.

HYDROSCOPIC SALT ON THE PLANT SURFACE.

The analytical results would indicate that calcium chloride as sueh
was on the grass, but if present no signs of it were observed on the
air-dried material. The samples were all thoroughly dry and not the
least evidence of any deliquescent substance on the surface was
apparent. It should be remembered, however, that the evidence
obtained in the examination of the organic acid indicated that the
ealeium salt was much less soluble than the sodium or potassium salt.
In all probability the greater part of the calcium in combination in
the solid phase and not in the form of calcium sulphate was present
as the calcium salt of the organic acid; and the greater part of the
sodium which was assumed above to be in combination with the
organic acid was in reality in combination with the chlorine, which
the analysis as stated assumes to be combined with calcium.

On the other hand, it has been noticed that this grass when grow-
ing in the field .is frequently covered with a moist, sticky substance,
which there is reason to believe is caused by moisture absorbed from
the air by the salts, but only in sufficient quantity to partially dis-
solve them, making a paste or gummy mixture. So that it is not so
improbable that calcium chloride is sometimes formed and is to be
found as such on the living plant.

SELECTIVE ABSORPTION OF SOIL CONSTITUENTS.

Another point brought out very strikingly by an examination of the
analyses is the relatively large amounts of both calcium and potassium
found in the leachings from the plants, when the proportion of these
elements in the water-soluble portion of the soil is considered. These
facts might possibly find an explanation in part in the lesser solu-
bility of the caleium and potassium salts of the organic acid and the
accumulation of such salts formed by contact of dust from the soil
with the acid. But such reasoning does not afford an explanation of
the enormously increased ratio between the chlor ions and the sulph
ions found in the plant leachings as compared with the ratio of these
substances in the soil. The relative absorptive powers of the plant
for these various constituents are probably the controlling factors.

5

It would seem desirable to give earnest attention to this subject
with plants grown under careful supervision in the field or laboratory,
as the evidence here presented indicates that the removal or cropping
of these plants for any purpose would result in taking from the soil
enormous quantities of desirable plant food and the consequent raising
of the proportion of undesirable elements in the soil.

FUNCTION OF THE ACID EXUDATION.

When the large amounts of soluble carbonates found in the soils
upon which these plants grow are considered, and when the disas-
trous corrosive action of this substance is remembered, the produc-
tion of the strong organic acid by the plant seems a wise protective
measure of nature. The tendency of sodium carbonate to outstrip
other salts in accumulating in the very top layers or crusts of a soil
and there corroding the root crowns of plants has been frequently
noted by all investigators of alkali problems. It would seem that
this organic acid is produced by the plant in the manner most favor-
able to its being brought into contact with the surface sodium ear-
bonate, partly converting this latter to the sodium salt of the acid
and partly, in all probability, to sodium bicarbonate, which, there is
strong reason for believing, is not itself so harmful to plant growth
as the normal carbonate.’

PHOSPHORUS IN THE PLANT,

In the attempts to identify the organic acid on Sample I, Distichlis
spicata, some leachings were obtained which contained a small amount
of organic matter mechanically suspended, as well as some in solution.
They were allowed to stand for several days in an Erlenmeyer flask,
the mouth of which was covered with an inverted beaker. A rapid
and voluminous growth of fungi was observed. On filtering off a
small portion of the solution after it had been standing a day or two
a decided though small amount of phosphoric acid was shown to be
present. No trace of this substance was found in freshly prepared
leachings of the plant. It would seem probable that it was formed
as a result of the action of organisms either upon dissolved organie

1 The especially pernicious effect on plants of carbonate of sodium is in ali prob-
ability due to the fact that this salt readily hydrolizes in water with the formation
of considerable amounts of sodium hydroxide, and it i: this latter substance which
is in reality responsible for its great destructive power. Sodium bicarbonate or
hydrogen carbonate, Na-HCO., might be expected to hydrolize to some extent
also, being composed of a strong base in combination with a weak acid; this would
be equivalent toa partial inversion to the normal carbonate. But in the presence
of so much carbon dioxide as is present in soils this inversion to the normal car-
bonate would be greatly retarded or altogether prevented. The normal dissocia-
tion of the hydrogen carbonate would then be very small indeed and any chemical
activity of the compound depending on the formation of ions would be corre-
spondingly smail.

76

matter in the leachings or perhaps upon the organic matter mechan-
ically suspended in the solution. From lack of material it was not
possible to determine the amount of phosphorus in the plant, but the
qualitative observations cited would indicate that it was present in
considerable amount. It should be observed that it was a constituent
of the readily water-soluble portion of the soil from which the plant
was taken in very small amounts, if, indeed, it were present at all.
Attempts to detect it by the phosphomolybdate method failed to show
a trace. The remarkable ability of this plant to take from the soil
solutions the mineral constituents it needed, in the presence of the
enormous excess of other readily soluble substances, is brought out
very strikingly in this connection. .

For the reasons here presented it would seem that this plant is
worthy of the serious consideration of the botanist and physiologist,
and is undoubtedly of very great economie importance.

ASH ANALYSES.

Ash analyses of all the plants considered in this paver were made,
in the hope that some conclusions might be drawn as to the inorganic
materials in the plants themselves, and as to how much, relatively,
was capable of being removed by leaching. These analyses will not,
however, be-presented, for it is obvious that they have no value what-
ever for the purposes here indicated. The mixture of salts on the
plants was so large in amount, and fused at so low a temperature, that
it quickly coated the organic matter, so that it was necessary to heat
to a very high temperature and thoroughly stir the mixture to obtain
anything like a thorough combustion of the organic material. This
resulted in a very great loss of the salts by volatilization, sodium
chloride and potassium chloride being especially important in this
connection. Further, the burning of either sulphates or chlorides of
the alkalies with organic. materials necessarily means the more or less
complete volatilization of the sulphur and chlorine, respectively, and
the formation of the corresponding alkali carbonates, a point often
overlooked in the consideration of ash analyses. As a consequence
of these factors, the results obtained would certainly be misleading.
It would appear, from the analyses of the ashes of the plants we are
considering, that much more of these soluble mineral constituents
can be leached from the plants than the plants ever contained,
which is an obvious absurdity. For this reason it does not seem worth
while to give these ash analyses any further consideration.

77 |

; _ SUAEDA INTERMEDIA AND ATRIPLEX BRACTEOSA.

TaBLeE XVIIL—Suaeda intermedii.

examination of the Suaeda intermedia and Atriplex bracteosa, respec-

SampleIV— | Sample V—
| Stems. Leaves.
GTATHS Gree LANGR =. 7 oS eee see ce eee See 7.61 14.35
Cubic centimeters of leachings ---..-..--....----...--------- 75 750
Percentage (mineral matter) leached out ------.-------.-. 14.73 23.80
Cubic centimeters N/20 acid,equivalent to 1 gram sub-
SiNOCD ~~ = 5a Soe ea ee een eee eee eos acy . 84 2. 67
: | Percent- Percent-
| Per- | 2 Per- <
| agein age in
gentage air-dried £eUtaee airdried
tion. Pace tion. sub-
ance. stance. F
or TR oe ke es hes ee ee ee 0.48 0. 071 0.15 0. 036
(Ee Se Sh en ns cee Se ee id 111 72 17 }
oT Pi 525 a ys ee RS 2 Se ee a ee eee 2.36 6. 239 56.18 13.375 |
Poe RE FB a Sn. sea Fee eee eo 7.20 1. 060 4.52 1. 075
SO, =f Seth oe ee Se a ee Se ee eS ene ee 1.43 | BA lik bal 206
wee bet Bee A Se ee Oe ee ee eee 47.78 7. 038 37.56 8. 938 |
100.00| 14.730) 100.00\ 23.800 |
A020 RS ee ee 1.62| .239 Bl 121
eed ee anne ee ead ons ae eace oeees . 00 000 . 00 . 000 |
bye 1+ poe se ee Re eee 2.66 | 392 2.35 . 559
wns 2). 22 Lae re ee ee ee ee 35 | . 057 . 64 152
aie a. tL ee ee ee eee 13.71 |! 2.015 8.61 2.049
(eh D4. 2 eee se ee ee OS ee ee ke 64. 84 | 9.551 52.33 | 12. 456 i
Be ee ee ee ee ee aa ee EE ee 16. 82 | 2.476 39.56 | 8. 463
|_—__—$_$— J ———§—l———— | __ _ _ ;
100.00 14.730 “100.00 23. 800 ;
/ /
TABLE XIX.—Afriplex bracteosa.
| Sample VI—- | Sample VII—
Stems. Leaves.
err DY ST i er eee Le ee ee ee | 21.49 17.79
Cubic centimeters of leachings --..._...-........-.-.--.--— 750 750
Percentage (mineral matter) leached out-.-.........--.---- 4.48 10.24
Cubic centimeters N/20 acid, equivalent tol gram sub-
Sus] 1 ii. e+ Sat SE Sa ee ee 1.19 3.61
Percent- | Percent-
| _ Per- : Per- mace
| centage oes in | centage | pac Ned
| distribu- 47 OT€e distribu-| 7 Cre
(epee sub- Hon. at sub-
; stance. stance.
Cg eee. LS os 8s See ot, | 2.321. 0.104 0.397 .0.040
sa wo eee ed een ans aed aes 2.05 . 092 3. 36 .d44
By eS ees gt Dee mre aw So ee ae oe sae eee 37.79 1. 693 41.30 4, 229
“UN = 5 es I ae eee | - 7.90 354 | 5.39 552
SL eee Se ers 5 en) Oe ee hee we 10 . 184 | 6. 60 . 676
SL 2 SaaS 2. ee | 45.84) 2.053| 42.96 4.399
4.480 | 100.00 | 10. 240
Ragen ois . 136
. 000
1%
125
5 1. 052
: 5. 485
2. 067
4. 480 100. 00 | 10. 240
In Tables XVIII and XIX are found the data obtained from an
.

0 ee eee eee
: «

78

tively. For the purposes of this paper they may very well be discussed -
together. Both analyses show the production by the plants of an: q

organic acid or acids strong enough to decompose alkali carbonates;
and that to some extent salts of this acid or acids, as well as the acids
themselves, accumulate on the plants. In both plants this acid organic
material is accumulated on the leaves rather than the stems, a situa-
tion which would seem more favorable for its being brought into con-
tact with the alkali carbonates on the surface of the ground.

The accumulation of considerable amounts of potassium is again a
noteworthy feature with these species. In both cases there is an
apparently greater proportion of potassium in the water-soluble por-
tions of the stems than in the leaves, when considered in relation to
the other elements present; but when considered in relation with the
air-dried material as a whole, the amount of potash is about the same
in both leaves and stems for each of these plants.

In the case of the stems of Atriplex bracteosa the conventional state:
ment of the analytical results as salts would indicate the presence of
calcium chloride as such, and on the stems and leaves of both the

~ Suaeda intermedia and Atriplex bracteosa considerable amounts of
magnesium chloride are indicated. That these salts were actually

presen’ as such, however, is negatived by the fact that the air-dried

saioie did not in any case show the presence of any notably deli-
qves ‘eat substance on their respective surfaces after being dried in

theoven. The conventional method of statement is again misleading,
as it the case of the Distichlis spicatu, discussed above. |

SUMMARY.

buon
:

‘rom the facts which have been presented in this paper the follow-
~ couclusions seem justified: ?

1 Vhat the plant species here considered can’ make a satistac-
tors seowth on soils containing relatively large amounts of soluble
Oonates.

«That this satisfactory growth is probably due, in large measure
at least, to the production and exudation by“%hese plants of consider-
able amounts of soluble organic acids capable of decomposing soluble
earbonates, and thus protecting the root crowns from the corrosive
again of hydrolized alkalies.

. That it appears certain that large quantities of the most valuable
lana foods are removed from the soil by these plants, and that in any
contemplated use of them, involving their cropping or removal from
the soil, this factor merits earnest consideration.

1 Acknowledgment is due Mr. Atherton Seidell for assistance in making the
analyses presented in this paper. .

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