The Seattle post-intelligencer. [volume] (Seattle, Wash. Terr. [Wash.]) 1888-1914, 1891-06-02
RESEARCH In BOTANY
Science Does Not Know Whence
Plants Get Nitrogen.
RECENT GAINS or KNOWLEDGE.
F1eshy Ercrescences Of Leguminous
Plants . Help to Their Growth
Benefits OF Parasites.

not yet succeeded In finally deciding the
question, Whence do plants obtain their
nitrogen7 Nevertheless, ii 10 a fact that
some plants are found to accumulate IN
their substance more OF this element than
can be proved to come from the soils In
which they grow, IL we accept the mere
analysis of these soils as showing what
stores Of nitrogen are at their disposal. IL
is relatively easy matter TO demonstrate
that in the available soil Of wheat held,
or of field of potatoes, clover, beans,
peas, ETC., so many pounds per acre OIL TINS
important constituent Of the crops exists
in the form of nitrates or oil am
monia salts, derived from the rocks
of which the soil Is composed, or
from the vegetable remains or manure
added TO the land, but numerous expert
ments have proved that whereas some
crops, such as wheat, oats and barley, for
instance, take away no more nitrogen
than can be thus accounted for; other
crops, such as peas, beans, clover and
other plants of the kind known as legum-
inous, remove something like twice as
much of this element from the land, guam
titles considerably in excess OF what Is
normally present in the soil, as nitrates
and similar compounds; moreover, the
puzzle Is rendered no simpler by the we'll
known experience that many Of the latter
plants do not leave the land poorer in nj
trogen as do the former, but that legumi-
nous plants enrich the soil with this ele-
ment, and have, therefore, come to be
called nitrogen accumulators, in contrast
to crops which distinctly exhaust the soil.
These facts have long been recognized
by botanists and agriculturists alike, and
no surprise can be felt that they should
have formerly assumed that these legumi-
nous plants must draw upon some other
source of nitrogen than the soil, and since
it is we'll known that the atmosphere con-
tains practically inexhaustible quantities
of free nitrogen, it seemed natural to con-
clude that the surplus Of that element in
leguminous crops was derived by the
plants from the atmosphere. Here was. of
course, a definite problem for solution,
and Investigations were conducted for the
purpose Of deciding the question once for
all
Experiments so arranged that every
source of external nitrogen but that of the
atmosphere was excluded, resulted in
proving that plants cannot assimilate the
free nitrogen of the atmosphere which is
everywhere in contact with them, and it
was suggested that the balance of nitrogen
in the leguminosea must come from con-
finuous additions to the soil OF compounds
of that element, such as the nitric acid
known to be produced in small quantities
under the influence of the electric dis
charge during thunder storms, and am
monia evolved by the decay of organisms,
and possibly by various other subtle pro-
cesses less understood; these compounds
exist at any one time only in minute guam
titles in the atmosphere, but they are
washed down in the rain, and soak into
the soil and accumulate there. The bora-
nists were by no means entirely satisfied
with this explanation, however, and since
IL was capable of being tested by comparing
the analyses of the contents of the numer-
Gus rain-gauges kept at various agricultural
stations, statistics we're prepared which
showed that there Is not sufficient OF such
compounds of nitrogen brought down in
the rain to make up the deficit, and SO the
problem was still an unsoived one.
So far as could be decided at the time, it
seemed clear that whereas most crops,
such as those of graminous plants, (wheat,
barley. hay. etc. derive the whole of their
nitrogen from compounds in the soil, or
brought into the soil by rain, the anom-
alous leguminous crops derive only part
OF their much larger quantities of nitro
gen from these sources, leaving balance
TO be accounted for; moreover, as said, the
latter crops, although they accumulate as
much nitrogen, do not exhaust the soil of
this element in anything like the same
proportion as the former. Somehow and
somewhere during the growth of the
leguminous crop the soil obtains nitrogen
in forms that are of use to the plants, and
ultimately the soil must apparently be en-
riched from the atmosphere.
In the meantime botanists had drawn
attention to some remarkable facts, which
no one dreamed of connecting with the
question of the sources of nitrogen in
vegetation until quite recently. 1t had
long been known that the roots of legumin-
Gus plants are studied more or less thickly
with curious fieshy excrescences, like
small tubers. and some few years ago il was
discovered that the cells of which these
tubercles are composed are densely filled
with multitudes of extremely minute
germs, so like bacteria that they have
since received the name 'tbacteroids I"
The first question that arose was
rs to the nature of these bac-
teroids or germs, and strange story
has resulted from the investigation. 1t
turns out that the bacteroids are true liv-
ing germs, so numerous and SO minute
that they are spread all over in the inter-
stices of the soil, in the air, in rivers. and
even in ordinary sand. If pea, bean or
other leguminous seed terminates in ortii-
nary soil or sand, exposed TO the usual
vicissitudes OF climate, its young roots in
yariably become infested by these ubioui-
tous germs. The germ attaches itself to
the root hairs of the plant, puts forth a
delicate process which enters the root, PEN
etrating from cell to CELL and at last
reaches its deeper parts. Once inside, the
injecting organism so excites the tissues
of the root that they grow out in the form
Of the fieshy tubercles referred to above
The process reminds one in fact to a GER
tain extent, of the formation of gall I'M
der the stimulus afforded by the puncture
OF an insect. For instance, the gals on the
roots of vines produced by the phylIorera
and other similar insects-but in the pres
eqt case the injecting organism is IN
dountediy OF vegetable nature, being one
OF those curious lower forms of fungi, in
she wider sense, which have been so much
studied of late years.
The leguminous plant is thus excited
into developing those soft, leshy, tuber-
cular masses of tissue, in which the fun
gus thrives and spreads rapidly, and in the
course of q few weeks or months, as the
case may be. myriads of these germs are
developed, many of which escape into the
soil. and these distribute themselves ali
over, whence they are washed into the
drains and rivers, or driven with dust into
the air. The ubiquity of these germs of
course explains that of the tuhercles. which
have now been sought for and found on
the roots of leguminous plants fresh
and IN herbaria from all parts of the world /:
just as certain bacteria and yeasts occur