512 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
the power of absorbing free nitrogen directly from the atmosphere with- 
out the assistance of the symbiotic fungus. In soil containing but little 
nitrogenous substance, the lupin is almost entirely dependent for its 
sustenance on the fungus. Trifolium pratense behaves in almost exactly 
the same way as the pea. Hence the yellow lupin is an exceedingly valu- 
able plant for increasing the nitrogenous contents, and in consequence 
the productiveness, of a poor soil. The author, therefore, contests the 
statement of Hellriegel * * * § that leguminous plants are entirely dependent 
on the symbiotic fungus for obtaining their supply of nitrogen from 
the air. 
Herr Frank also states that some plants not belonging to the 
Leguminosae, as the oat, buckwheat, asparagus, rape-seed, &c., have the 
same faculty of obtaining free nitrogen from the atmosphere, with- 
out the assistance of a symbiotic fungus, and hence of increasing the 
nitrogenous constituents of the soil. 
Sources of Nitrogen in Leguminous Plants.f — The most recent 
experiments of Sir J. B. Lawes and Dr. J. H. Gilbert show that the 
nodule-bacteria of Leguminosae have no power of fixing free nitrogen 
while in the soil, but only when carrying on a symbiotic existence in 
the roots of the plant. They may, however, bring the organic nitrogen 
into an available form, as in the case of mycorhiza and of the fungus 
of fairy rings. The free nitrogen appears to be fixed in the course of 
development of the organisms within the nodule. A good deal of the 
nitrogen of leguminous crops is also taken up in the form of nitrates. 
The experiments further show that soil which is quite exhausted as far 
as the growth of one leguminous crop is concerned, may grow very 
luxuriant crops of another species even of the same family. The 
authors give a resume of the observations of previous observers. Thus, 
while experiments with yellow lupins gave very striking results, those 
with blue lupins entirely failed. Gleditschia , which belongs to the 
suborder Caesalpinieae of Leguminosae, proved altogether indifferent to 
infection from the nodule microbes. 
Transpiration and the Movement of the Stomates.f — Prof. A. Aloi, 
replying to the criticisms of Baccarini, repeats the conclusions to which 
his own observations have led him, viz. that a larger amount of transpi- 
ration always corresponds to a larger opening of the stomatic fissure ; 
that a smaller amount of transpiration always corresponds to a narrowing 
or to a complete closing of the fissure ; that the action of light has no 
effect in causing the opening of the stomate when the necessary moisture 
is wanting in the soil ; the stomates regulate transpiration by their 
movements. 
Tension of Gases in the Stem.§ — Herr K. Pappenheim describes 
an elaborate apparatus for determining the tension of gases contained 
within the alburnum of Conifers {Abies excelsa). The following is a 
summary of the more important results at which he has arrived : — The 
air contained within the alburnum which was not under the immediate 
* Cf. this Journal, 1889, p. 781. 
t Journ. R. Agric. Soc., ii. (1892) pp. 657-702. Cf. this Journal, 1890, p. 634. 
% Malpighia, v. (1892) pp. 419-26. 
§ Bot. Centralbl., xlix. (1892) pp. 1-10, 33-40, 65-74, 97-106, 161-8 (1 pi.). 
