334 
result was due to the fact that in the previous year the upper river- 
tributaries had in October begun to rise, while in December, 1906, 
they were still dried up, and navigation at a standstill. 
The value of the Rubber before shipping, i.e., before duty had 
been paid on it, probably exceeded ^9,500,000. 
W. J. GALLAGHER. 
SCIENCE NOTES. 
Fixation of Nitrogen by Leguminous Crops. 
From an article entitled ‘Recent Progress in the Practice of 
Green Manuring/ which appeared in the Bulletin of the Imperial 
Institute , the following particulars, relating to the fixation of nitrogen 
by leguminous crops, and the advantages of such crops for use in 
green manuring, have been abstracted : — 
Green manuring improves soils on which it is carried out, in 
several ways. Vegetable organic matter is added, which not only 
provides plant food, but also improves the mechanical texture of 
heavy soils, by lightening it, and making it more open. Further, 
the organic acids produced in the decomposition of this vegetable 
matter act as solvents upon the soil constituents, and so render more 
material available for plant nutrition. 
Probably, how r ever, the most important advantage consequent 
upon green manuring is that which follows when a leguminous crop 
such as peas or beans is the ‘ green manure,’ for by means of such 
a crop, nitrogen from the air is fixed, or converted into nitrogenous 
compounds, and stored up in the soil, where it is available for the 
succeeding crop. 
About twenty-five years ago, it was ascertained, as the result of 
experiment, that leguminous plants were able, under some circum- 
stances, to extract a certain quantity of nitrogen from the air, and to 
make use of it in their tissue building.. The actual method of fixa- 
tion of the nitrogen by these plants,' however, was not understood until 
1886, when HELLRIEGEL and WlLFARTH furnished an explanation, 
as the result of experiments and observations made by them. Th'ey 
found c that whilst most plants, when raised in sand free from nitrogen, 
ceased to grow after the reserve nitrogen contained in the seed itself 
had been absorbed, seedlings of leguminous plants sometimes con- 
tinued to develop after passing the stage of dependence upon this 
reserve of food. Obviously, the nitrogen these plants daily added 
to their tissues was supplied by the air, since it could not be obtained 
from the soil. Messrs. HELLRIEGEL and WlLFARTH noted how- 
ever — what had not yet been remarked by other observers — that in 
all cases where continued growth of the leguminous seedlings did 
occur, nodules or swellings were to be found on the roots. It was 
further found that leguminous plants, germinated in sterile sand, 
soon ceased to grow well, but that if a little water extract of a good, 
