1895.] Botany. 371 
BOTANY! 
Nitrogen Fixation in Algz.—The following results of research 
on this subject since 1892 are thus summarily stated in a recent num- 
ber of Nature. They are chiefly derived from the papers of Grosso- 
witsch, Schloessing, Laurent and Koch. Their observations shed much 
light upon the question of the relations exisiting between Algæ, micro- 
organisms, and atmospheric nitrogen. They show :— 
(1) That at least two Algee—C d Stick possess no 
“ fixing ” powers in themselves. 
(2) That many Algæ, taken together with certain microörganisms 
of the soil, do possess the power of assimilating atmospheric nitrogen. 
(3) That this power is much increased by the addition of such 
organic substances as sugar. 
It should be noticed that among the ten cultures used in the second 
set of experiments, only two contained definitely isolated algal species, 
viz. the cases of the two cultures of Cystococcus and soil-bacteria. 
It was just in this instance, moreover, that it had been shown that 
the Alga itself had no capacity for fixing atmospheric nitrogen. Ac- 
cordingly there could be little doubt that it was through the agency of 
the mieroorgan)eys that the “fixation” had taken place in these latter 
cultures. 
The experiments of Laurent and Schloesing had shown that if in a 
culture of Algæ and bacteria endowed with “ fixing ” powers, the Algæ 
were destroyed, the bacteria lost partly, if not entirely, this capacity, 
which the mixture had possessed. This pointed clearly to the fact that 
there was some close relationship’existing between the Algæ and micro- 
organisms. 
There are many facts which seem to indicate the nature of this rela- 
tionship. 
Berthelot found that the nitrification of the soil only took place as 
long as organic compounds were present; if these were exhausted, the 
nitrifying process ceased. Gautier and Dronin also showed the im- 
portance which organic compounds have with respect to nitrification. 
Kossowitsch’s own experiments, in which the advantage of adding 
sugar to the culture was shown, also point in the same direction 
From such observations as these, Kossowitsch concludes that the 
relationship which the Algæ bear to the microérganisms is one con- 
1 Edited by Prof. C. E. Bessey, University of Nebraska, Lincoln, Nebraska. 
