564 Ward. — Some Methods for Use in the 
glass dishes. With species of Oscillaria and of Palmetto , , 
certain Protococcoideae, & c., the author has observed growth 
in hanging drops of this silica-jelly medium under high 
powers, and has seen sufficient to make it hopeful that even 
Diatoms may be cultivated this way ; and it is not impossible 
that some modification of the process could be utilized for 
the culture of marine Algae. 
Another device is as follows : — 
3. Shake the Algae up in the nutritive solution and rapidly 
mix with sterilized plaster of Paris, and pour into dishes. 
The fixed Algae grow in situ in some cases, but others appear 
to be too sensitive for such treatment. 
Experiments have also been made as follows, with some 
success : — 
4. The Algae are shaken up in the culture medium, and 
a large quantity of lime-water quickly added. Then carbon 
dioxide gas is passed rapidly through, and the Algae are 
thrown down with the precipitate of calcium carbonate ; 
this is poured into dishes as if it were plaster of Paris. Perhaps 
this method could be utilized in the study of calcareous Algae, 
but with some forms it appears too drastic. Baryta seems 
to act as a poison, and cannot be substituted for lime. 
It is clear that if once we obtain a pure colony on a glass 
dish, a trace fished out with a needle may be used to start 
other cultures. Season, temperature, intensity of light and 
other factors, are of importance in these matters. 
As an illustration of what may be done with the hanging 
drop culture I take the following example : — 
On August 21 a quantity of Oscillaria — O. tenerrima (Ktz.) 
apparently — was shaken up in Knop’s mineral solution, added 
to silica jelly and poured with a drop of sodium chloride 
into a plate, where it soon set. On the 22nd I made a hang- 
ing drop of a small portion of this, and fixed a small piece 
of the Alga under a 4 mm. dry apochromatic lens with 
No. 2 eye-piece with micrometer. The piece measured 1 3-5^ 
long x 2*25 1 u broad, and next day showed no perceptible 
change. Nor could I detect any growth on the 24th, or 
