8o4 
THE TROPICAL AGRICULTURIST. 
[Juke r, 1^4. 
Now come the other aspects of the controvers)' 
which raging chiefly around the question as to ex- 
actly where and how this gaseous nitrogen is fixed. 
Oliviously several possibilities could be suggested. 
(1) The gaseous nitrogen could be conceived as 
directly fixed by the plant which gains in nitrogen — 
as absorbed by the protoplasm of the living cells 
exposed to the air— e.^., the cells of the leaves of 
the leRUTiuous plant, or those of the algae on the 
surface of the soil. This view is actively maintained 
by Frank and a few supporters, who go as far as 
is possible in this direction, and really again raise 
the old question which originated with De Saussuve. 
and was rightly regarded as refuted by Bonssingault 
and Lawea and Gilbert. 
(2) The gaseous nitrogeu could be conceived to 
be fixed in the siil by means of bacteria or lower 
algse (we have seen these are left indefinite), and, 
when it has been converted into ni r.igenous com- 
Eounds of some kind in the soil, eventually absorbed 
y the roots of the leguminous or other higher 
green plant in the ordinary course of events. The 
principal champion of this v ew is Berthelot, who 
claims to have proved that certain soil-bactcia, ai d 
also the organisms of the leguniinoui root-nodu'es, 
have the power of fixing the free nitrogen of the 
air, and so enriching the soil in nitrogenous compoui ds. 
In this connection, of course, the whole question 
of nitrification and de-nitiitication in ihe soil will 
no doubt be involved with the question of the 
fixation of free nitrogen from the atmosphere. 
(3) The fixation of the atmospheric nitrogen could 
be conceived of as a powerful act of the machinery 
of the leguminous plant, urged to the necessary 
expenditure of energy by the stimulating action of 
the symbiotic organism in its roots. Tlii'j view, held 
especially by Hellriegel, Prazmowski, and others, 
is also shared by Frank, who believes that it is only 
in their being thus stimnlafed to greater activity 
that the legumiuoste differ from many ofier 
plants, which, he says, also fix the atmospheric 
nitrogen directly, but to so much \eai an extent 
that the experimental proof of their power to do 
it is far more difficult. 
(4) Another possible view is that the loot-organisms 
act merely as accumulators of nitrogenous material, 
which has been derived from atmospheric nitrogen 
fixed and combined in the soil, by physical or 
chemical processes, or in the open ground by the 
action of aoil-orgauisms ; and the leguminous plant 
benefits by devouring (if we may employ this word) 
the bacteroids eventually, and profiting by their 
stores of nitrogenous material. 
Let US now take these four pos-sibil tie' in order, 
and examine them a little more in detail. 
The first view rests almost entirely on the state- 
ments of Frank, of Berlin, who brings forward a 
number of experiments which in his opinion show 
that many higher plants, in addition to the 
leguminosoB, are capable of directly assimilatii g the 
free nitrogen of the atmosphere. For instau' C, 
FraTik gives results sbovviug that oats, buckbeai p, 
spurrey, tornips, mustard, potatoes and Norway maple 
are all capable of fixing atmospheric ni'rogen. 
Most of Frank's experiments wera made in the 
open air, the pots of plants being simply sheltered 
from rain; but in some cases, he sifiims that he 
got positive increase of nitrogeu with must ird-plants 
under bell-jars, properly shut off from the outer 
air, aud through wh ch purified air was drawn. 
Apart from these latter, and in spite of Frank's 
assertion that the quantities of combined nitrogen 
in the air are so immeasurably small that they 
may be neglected, it seems fair to object that, in 
the present state of science, we cannot trust experi- 
ments in the open air to decide such a point ; while, 
with regard to tlie experiments with mustard, it must 
not be forgotten that not only the eld results of 
Boussingault and Lawes andGiliert are entirely and 
emphatically opposed to them, but the exceedingly 
careful lecent experiments of Schlcssing and Laurent, 
made with all modern appliances and methods, showed 
the contrary — no signs of fixation of nitrogen 
cuuld be obtained in oats, tobacco, cress, mustard, 
cabbage, sporrey, and potato, the very plants Prank 
used. 
Frank r. ph'es th»l completely Borai«1 pi ti t - cannot 
le ^rowu under such tloi^'y covcreH g sSj Tea cl« as 
tlu'fe expeiimen ers u e, lu' he acct-j ts their p<eiliT« re- 
ta\ B iu rI) c se'. Frank's ronii miuu i. that tbe 
plai/ts nu t be veiy vigmou', and n' ar it* tuaturiug 
p 'in^, b<fore it has power to eo rg< tic*ll} mj zs au4 
"fix " the atmcspherio uiir Jt^'' ; but (withont e'e'jiog 
•ha' it is po 6ibl« that the utm> et vigur miiy Lot 
Leaf yet attainab'e uude' the ccd liiioua newssary 
for culture in closeilglas.s re ceptsc es o' liiui ed opati y) 
it is itppos^ible to overlook'the danger that lu fxiie i- 
ments in the open air, the 'im • which nia«t uecef&iirily 
elap e be'ore Fr uk's critic I period of maturity oo the 
pirt of thi« plunt is reac'^ed, is Iodk enough f.r 
all forts of dis urhiog inlln nc«B to c m ■ i , e»|i daily 
if any kind of'fixatioj" ii the Boil, sucli a» lletih :ot 
asserts, really occurs; tbe roo -h»ii s would lake uji, 
a id ti.e plant absorb, nilrrg uous bodi <> as f»t>t as 
tliey Hoie formed in the soil arouijd Ibem, while 
there w uld be anrpli (iiuj for the developiceut of 
many gencrilioni ot micr<.-or(.a istcs in th < uiid uui. 
In \iew of the tenacity with which the belief ia 
a d rei t absorption of atmotspht ric nitrogen lis che- 
rishrd by many foresters and agncultorieta, it seems 
imperative that critical experiments should be per- 
.scvered in; as matters stand, we cannot accept 
Frank's position as proved, or even as rendered 
probable. 
The possibility mentioned above as an explanation 
of t' e danger of accepting Frank's results would be 
rendered a certainty if the recent researches of 
Laurent and Schloosing, Koch and Kossowitsch, and 
Berthelot, in part sopporting earlier statements by 
Frank himself, turn out to have betn properly 
interpreted. 
Laurent and Schloes'ng— and their results are con- 
firmed by Koch and Kossowitsch — declare that 
sterilised sand, devoid of nitrogenous material, when 
covered with a growth of certain green and blue- 
green algae, probably mixed, however, r. ally does 
"fix" the atmospheric nitrogen, and gains in nitrogen- 
compounds, but only if the algal growth is freely 
exposed to the atmosphere iu the closed chambers 
employed. These statements confirm earlier, but 
less definite, experimental results by Frank ; and 
the latter has recently expressly stated that certain 
fungi — e.i/., Penicillin m cladosiiorwidts — can flourish in 
a medium to which no nitrogen but that of the 
atmosphere has access. 
Berthelot goes further, and claims to have esta- 
Ijlished that several species of soil-bacteria aud fungi, 
inc'uding the fungoid organism of the leguminous 
tubercles cultivated separately, can " fix " free nit- 
rogen ; and if the analyses of the small quantities 
of materials in his flasks survive the criticitm of 
the chemists, it seems difficult to refuse credence to 
the views he puts forward ; but, as iu most of 
these cases, it is the enormous difficulties of analyses 
which lie at the root of the matter. 
Moreover, different observers differ considerably 
on this question. Beyerinck, while regarding it as 
probable that the uodule-organis'ns " fix " atmos- 
pheric nitrogen, admits that he does not prove it ; 
and in Laurent's special investigation iuto this q jes- 
tion, he left it also uncertain ; while immendorf 
failed to satisfy himself that these organisms can 
florish without organic compounds of nitrogen ; and 
F ank insists that they do not thrive at all without 
organic nitrogenous food-materials. Moreover, it 
must not be overlooked that other observers, e.g., 
Gautier and Drouin, have given evidence p inting 
to possible phenomena of "fixation ' of nitrogen by 
compounds of iron and other substances clinging to 
particles of the sand employed, which may interfere 
with the accuracy of conclusions drawn from ex- 
periments where sterilised soil in the open air is 
concerned. 
AVhen we reflect how very minute these organisms 
are, and what excessively small quantities of nitrogen 
they need for their life-purposes, we cannot be 
surprised at the difficulties met with in these investi- 
gations. But, however far from proved we may 
