670 A rber. — On the Effect of Nitrates on the 
greatly with the nature of the salt, and with different Algae. 
Loew and Bokorny 1 found that Spirogyra flourished better 
in sodium nitrate (NaNO s ) than in potassium nitrate (KN 0 3 ). 
The presence of KN 0 3 induced an abnormal amount of 
starch-formation, but quickly resulted in the death of the 
Alga. Ammonium salts were found to be directly injurious 
to Spirogyra ; an addition of o-i per cent. NH 4 C 1 quickly 
caused death. Stange 2 says that Spirogyra, Cladophora, and 
Zygnema will never tolerate more than 1 per cent. KN 0 3 , 
and Oscillaria 1-5 per cent. ; while species of Pleurococcus 
have been observed to thrive in 12 per cent. KN 0 3 . In the 
higher plants, Stange also found that a solution of KNO s 
gave disastrous results in many cases, and Halophytes were 
generally quickly killed by a solution containing o-io gram- 
molecules per litre KN 0 3 . Quite recently Jacobi 3 has shown 
that potassium nitrate decreases the assimilation of submerged 
plants, such as Elodea and Myriophyllum. 
The nitrate which occurs in sea water is magnesium nitrate, 
and this is undoubtedly the sole source of nitrogen to such 
Algae as Ulva. The amount is exceedingly small, about 
•002 per cent. During the course of this work I made a con- 
siderable number of experiments with four nitrates, viz. those 
of potassium, sodium, magnesium, and ammonium, each being 
used separately. Two series of experiments were made in 
each case, with the exception of ammonium nitrate. In one, 
a certain percentage of the nitrate alone was dissolved in 
distilled water, in the other, in sea water. 
(A) Potassium Nitrate. 
The following preliminary experiments show very well the 
disastrous effect of the presence of potassium nitrate on the 
power of carbon-assimilation. In Experiment I, the distilled 
water contained 1 per cent. NaCl; in Experiment II, 1 per 
cent. KN 0 3 in addition to 1 per cent. NaCl. 
1 Loew and Bokorny (’87). 
3 Jacobi (’99). 
2 Stange (’92). 
