[Vor. 1 
230 ANNALS OF THE MISSOURI BOTANICAL GARDEN 
Brandt (7), however, attaches little or no importance to 
Reinke's view, and maintains that the nitrogen content 
of sea-water is determined by a balance between the activity 
of denitrifying bacteria, on the one hand, and the great amount 
of nitrogenous material carried to the sea by the rivers, on the 
other. Brandt (5, 6) considers that the nitrogen content of 
sea-water is аба minimum" and is the limiting factor in the 
production of marine organisms. Considering especially the 
plankton life, he finds that the amount of plankton is propor- 
tional to the nitrogen content of the water, and correlates the 
comparative poverty of tropical seas in plankton life with the 
relatively greater activity of denitrifying bacteria in the warmer 
waters. 
More recently Pütter (14) bas reported that analyses of the 
water from the Gulf of Naples give per liter .18 mg. of nitrogen 
in nitrates and nitrites, and .56 mg. in ammoniacal nitrogen. 
Furthermore, he claims that these figures represent less than 
half the total combined nitrogen actually present in sea-water. 
In his opinion there is no need for considering the nitrogen 
content to be at a “minimum” since it is present in greater 
concentration than the carbon dioxide. It is impossible to 
say which of these views is the correct one, and further work 
in this field is much needed. 
The above named authors incidentally assume that nitrogen 
is available for the alge only in the form of nitrates or ammo- 
nium salts. This is entirely an a priori assumption, as no data 
are offered in support of such a view. On the contrary, it 
seems more likely that the alge can use many organic ni- 
trogen compounds. This would seem probable in the light of 
recent work which has been done on the fresh-water alge. 
In regard to the nutrition of the fresh-water forms we have 
departed far from the old idea that green plants are strictly 
autotrophic. Thus, by the work of Beyerinck (3), Charpentier 
(8), Chick (9), Artari (1, 2), and others, it has been established 
that many of the fresh-water alge have, with respect to nitrogen, 
distinct saprophytic tendencies,—preferring organic to inor- 
ganic nitrogen. Artari, especially, has shown that several 
alge (Chlamydomonas, Stichococcus, Chlorella, Scenedesmus, and 
others) can grow and retain the chlorophyll under completely 
