The Seattle post-intelligencer. [volume] (Seattle, Wash. Terr. [Wash.]) 1888-1914, 1891-06-02


weakness and inanition Of peculiar kind,
and mar soon die of starvation; II, on the
other hand. the plants are growing IN sim
ilariy st9ilized media, but carefully IN
fecfed at the roots so as TO insure their
being penetrated by the fungus. and so pro-
ducirig the tubercles, they flourish exceed
ingly, and may even DO better man piandas
nit Of but one Interpretation, namely,
that in some way or other the presence OF
THE tubercies land therefore Of the infect
ing fungus which excites their develop
ment) is of advantage TO the ieguminous
plant, and the question arises, howY TX.
detrimental investigation have recently leo
TO the suggestion that in some way or
other the fungus helps the higher plant
to obtain its excess Of nitrogen: and there
Is apparently much to be said for this
view
Two difficulties, of course, present them
selves: In the first place il Is asked, how
can the fungus be thus parasitic. as 1t were,
in the roots of the plant and still not IN
lure il; and, secondly, by what means can
such organisms as these minute and loWly
germs. abundant though they are, obtain
the free nitrogen from the air. when it has
been established that the higher plant -
unable to directly assimilate that gas
These questions are undoubtedly peril
nent, but it appears with respect to the
first of them that this is by no means the
only example of the symbriosis, or mutual
ism of two organisms, known to pbysi-
ologists: both in the animal and vegetable
kingdoms cases are well understood where
animals or two plants have taken to Nv
ing together IN common, and deriving
mutual benefit from the arrangement, or,
rather, have established the symbriosis,
because il is advantageous TO both. 10
mention one illustration only: The we'll
known ichens of our rocks and walls are
cases in point. The Iichen is now known
to be conjoint organism, consisting of
green alga enveloped in meshes Of a color
less fungus; the aigs provides carbona-
ceous food from the atmosphere and the
fungus contributes other constituents to
the common table at which both feed.
Hence the botanist sees no difficulty IN
regarding the leguminous plant as the
great carbon provider; If the fungus In IT'S
roots can be shown to contribute Iair
share of the entertainment in some other
way, and recent researches render 1t very
probable that it does so.
In some cases the higher plant has been
shown to take up some of the substances
formed in the tubercles, probably IN part
the dissolved remains of the germs, and IL
is even alleged that mighty vengeance IS
executed on the more humble guest when
the higher plant grows big and strong
enough to absorb the fungus. Be this as 1t
may, the contents of the tubercles-i. e.,
the substances of which the germs are
composed-are remarkably rich in nitro
gen, and if the leguminous plant absorbs
any considerable proportions OF these, as a
tax provided by the fungus TO pay for the
advantages il obtains by the alliance. then
all difficulty as to the high percentage of
nitrogen in the mature plant disappears.
But land this concerns the second ques-
ton mooted above) it is one thing to prove
that the Ieguminous plant enriches itself
in. nit a. faf no h
stance of the fungus in the tubercies, and
quite another TO suggest satisfactory
explanation as TO the processes by which
that fungus has accumulated this nitrogen
from any other source than compounds
already existing in the soil. In fact,
nitrogen of the atmosphere is
only removed from the leguminous
plant to the fungus. If we assume
that the latter can in some way enable the
soil to gradually fix nitrogen, in the form
of some compound which the fungus can
absorb and convert into plant substance,
then it is easy to see not only how the
higher plant obtains its large supplies OF
nitrogen over and above those provided by
the nitrates of the soil itself, but also to
explain why the land is actually enriched
in nitrogen by the leguminous crops, the
decaying root-tubercles of which shed
myriads of the germs in all directions into
the soil.
Here, however. we stand face TO face
with the great difficulty of the entire con-
troversy. The facts of the symbriosis of the
plant and the fungus are confirmed and
established, as are also those OF the large
nitrogen requirements of the leguminous
plant; moreover, it seems impossible to
go behind the experimental proofs that
free nitrogen is not directly assimilated
by the higher plants. But the soil i'm
pregnated with germs acquires nitrogen,
according to the recent experiments, and
the only conclusion drawn from this is
that in some way the fungus enables the
soil to obtain this. How, is a mystery.
Nitrogen is particularly inert body, by
no means readily forced into combination
with other elements, and peculiarly apt to
escape even with explosive violence when
once united, and no plausible hypothesis
as yet exists to account for the alleged
fixation of free nitrogen by the soil, and
until this is forthcoming the above ques-
ton remains unanswered. Meanwhile at
tention is concentrated on the tubercles of
the roots, and especially on the remarkable
fungus they contain, the life history of
which is as interesting as the results of it
are alleged to be important.
PROF. III. MARSHALL WARD, E. r. s.