Marine Bacteria. 
and fell roughly into four classes. (1) Those that quickly reduced 
nitrates and nitrites to free nitrogen without the formation of 
ammonia. (2) Those that easily reduced nitrates to nitrites, but 
the latter only with difficulty and with the formation of a certain 
amount of ammonia. (3) Those that could not reduce nitrates to 
nitrites, but reduced nitrites slowly. (4) Those that were unable 
to reduce either nitrates or nitrites, and were also incapable of 
assimilating them. Of the forms found only a small number played 
an important part in denitrification, of which three, having a 
specially energetic power of reduction, were more closely studied 
and described. The supposition, that the denitrifying bacteria 
found might be only land forms accidentally present in the sea, 
was recognised, but when investigated was found to be untenable. 
The conditions necessary for the process of denitrification 
were investigated in some detail. It is shown that the process 
occurs under certain conditions of temperature, of supply of oxygen 
and of nutrition by means of organic material. The first two 
conditions are such as would be easily satisfied in the natural state 
in the sea. The amount of nitrogen reduction was found, however, 
to vary both with the kind and quantity of carbon-containing food 
material. Mannite was found to be the most active substance in this 
connection, but it required about four times the quantity of mannite 
to bring about the reduction of a given quantity of nitrite. 
The conclusion to be drawn from these observations is that 
denitrification takes place in tbe sea, where there is a sufficient 
quantity of organic material. It will therefore probably be found to 
occur near the shore where there is a quantity of detritus from the 
land; but whether such a process plays an important part in 
relation to the nitrogen circulation of the ocean, must be left to 
future researches to decide. The occurrence of denitrification 
to any considerable extent in the open sea seems somewhat 
improbable; there is in fact, as yet, no evidence of the presence of 
denitrifying bacteria in such waters. V. H. B. 
MISCELLANEOUS NOTES. 
Mh. Buysman’s Herbarium Specimens. 
Mr. Buysman writes that he has reduced the price of his 
herbarium sheets, described in our last issue, to sixpence each. 
