388 Boos ALLEN: 
Previous work dealing with the culture of diatoms had been done 
mainly by the French bacteriologist Miquel. Miquel himself investigated 
principally fresh-water diatoms, but he showed that the methods he 
employed could be used also for marine forms, his experiments in this 
direction having been made chiefly with shore and bottom species. My 
own work, in which during the earlier stages I received much assistance 
from my colleague, Mr. E. W. Nelson, has dealt mostly with the floating 
or Plankton diatoms, which are much more delicate organisms to deal 
with than the fresh-water or marine bottom forms. 
Miquel showed that fresh-water diatoms could be most successfully 
grown When to the water there was added a very small quantity of certain 
inorganic salts, together with a small proportion of soluble organic 
matter, prepared by making an infusion or maceration of straw, bran 
or some other vegetable substance. 
The inorganic salts, which Miquel considered necessary, were the 
following :— 
Magnesium sulphate 
Sodium chloride 
Sodium sulphate 
Ammonium nitrate 
Potassium nitrate 
Sodium nitrate 
Potassium bromide 
Potassium iodide . 
Sodium phosphate 
Caleium chloride 
Ferric chloride 
Of these salts the most important were found to be the nitrates, the 
phosphate and the iron salt, a result which agrees with what we know 
of the requirements of plant-life in general. These three substances, 
especially the nitrates and phosphate, are as is well known largely used 
by farmers as artificial manures. 
In order to grow marine diatoms, Miquel added to sea-water the same 
salts which he had used for growing fresh-water diatoms. Our experiments 
have shown, however, that it is by no means necessary to add all these 
salts to sea-water in order to get good cultures. Quite as good results can 
be obtained by the addition only of Potassium nitrate, Sodium phosphate 
and Iron chloride, the two latter being made into solution with calcium 
chloride and hydrochloric acid, according to a special method described 
by Miquel. 
If sea-water which has been obtained near the coast is used as the 
