ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
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relation to the deteriorating effect of placing them in an atmosphere 
devoid of carbon dioxide. The power of developing inactive leaves is 
not constant in the same species, being dependent on the availability of 
the reserve-food for this purpose. Material constructed in active chloro- 
phyll areas, and stored in special organs, may be transported to inactive 
chlorophyll organs in some plants in light and in darkness, and may be 
used in such a manner as to allow of the perfect development of those 
•organs. It is possible for some plants to form perfect leaves in darkness ; 
some when a portion of the stem only is darkened, and others when the 
•entire plant is darkened. Placing a leaf under such conditions that it 
cannot construct food-material, sets on foot the specific regulatory 
mechanism of the organism in such a manner that the plastic material 
may be withdrawn and the organ cast off. An exaggerated development 
of the petiole in darkness may be induced by this mechanism. 
Recent Literature relating to Leguminosse Tubercles and the 
Fixation of Free Oxygen. — Prof. Stutzer * reports on some of the most 
recent papers on the root-tubercles of the Leguminoste. 
Herren F. Nobbe and L. Hiltuer | continue their experiments on the 
adaptability of root-tubercle bacteria of unlike origin to different genera 
of Leguminosae. The experiments showed that an effective inoculation 
was obtainable with certainty only when inoculations were made from 
like species. From these experiments two important conclusions are 
arrived at, namely, that the tubercles have no influence so far as aerial 
growth is concerned, so long as the plants obtain sufficient nitrogen 
from the soil, and that, directly the soil-nitrogen begins to fail, those 
Leguminosse which are devoid of or possess only imperfect tubercles show 
their want of oxygen ; hence the leaves of the Leguminosse can hardly 
be considered as organs for assimilating oxygen. 
M. Gonnermann J obtained pure cultures of tubercle-bacteria in a 
medium composed of 100 grin, of expressed lupin juice, 10 grm. gelatin, 
and 3 grm. meat pepton. 
Salfeld § observed that burnt chalk prevents the formation of tubercles 
on peas, but B. Tackc,|] who has also investigated the question, finds 
that Salfeld’s results must be due to some other cause, for chalk seems 
to favour the formation of root-tubercles. ; 
Physiology of the Root-Tubercles of Leguminosse. H — From the 
results of a series of experiments carried on for two years in the S. of 
F j ance on a number of different sjiccies of Leguminosie, M. C. Naudin 
doubts the correctness of the prevalent hypothesis that the bacteria of 
the root-tubercles have the power of absorbing the free nitrogen of the 
atmosphere, or that they are of advantage to the host-plant. He finds 
that some species thrive quite as well in sterilised soil, the seeds some- 
times germinating earlier, and producing stronger plants, than those 
sown in ordinary soil. The plants grown in sterilised soil had some- 
times a large number of root- tubercles, sometimes only a few, sometimes 
* Centralbl. f. Bakteriol. u. Parasitenk, 2 tc Abt., ii. (189G) pp. G50-3. 
f Landwirt. Versuchstat., xlvii. p. 257. % Landw. Jahrb." xxiii. p. 652. 
§ Deutsche Landw. Presse, 1894, No. 83. 
Ii Mitt. d. Yereins. z. Forderung d. Moorkultur, 1895, p. 3S9. 
% Comptcs Eendus, cxxiii. (1896) pp. 666-71. 
