486 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
It is now a very easy task to stain such objects, and mount them in 
glycerin, glycerin-jelly, or balsam. If they are mounted in balsam the 
preparations should be successively treated with alcohol, xylol, and 
lavender oil. Care must be taken lest the organisms get dry dining the 
process. 
Fixing and Preparing Freshwater Algae.* — F. Pfeiffer R. v. Well- 
heim recommends the following process. The fixing fluid is composed 
of equal parts in volume of 40 per cent, formol, pyroligneous acetic 
acid, and methyl-alcohol. After decanting the greater part of the water 
from the alga, the fixing fluid is added, and must be at least double in 
volume of the water that remains. The algae may remain in this fluid 
for weeks or months. If the alga is of a gelatinous character, it must 
be transferred from the fixing fluid into strong alcohol ; and this must 
always be done before examining or staining. 
Algae fixed in this way may be stained by any of the familiar colouring 
reagents. Very favourable colouring solutions are the following : — 
(1) 100 ccm. of 50 per cent, alcohol, with 2-3 ccm. of iron chloride 
solution in 90 per cent, or in absolute alcohol ; (2) A concentrated 
solution of perfectly pure carmin-acid in 50 per cent, alcohol. Before 
staining the object must lie in 50 per cent, alcohol. It must then remain 
in solution (1) for at least 4—6 hours, and be then freed from the excess 
of iron chloride by 50 per cent, alcohol. A few drops of solution (2) are 
then added ; and the staining is completely effected in a few hours. 
The object is next placed in 95 per cent, alcohol, and then transferred 
to the imbedding substance. 
By this process the structure of Spirotsenia trabeculata, and the 
honey-comb structure of Oscillatoria princeps , are very well shown. 
Preparing Parasitic Fungi.| — Prof. A. N. Berlese adopts the fol- 
lowing method of preparing microscopic fungi parasitic on leaves. The 
special advantage is that the observer can at once detect whether the 
fungus is in the stage desired for examination, without waiting the result 
of a long and tedious process. 
Pieces of the leaf infected by the parasite are placed in absolute, or 
in 96 per cent, alcohol, or in concentrated picric acid, or better, in a 
mixture of 15 ccm. 0*5 per cent, chromic acid, 6 ccm. 1 per cent, osmic 
acid, and 1 ccm. glacial acetic acid, and then in concentrated nitric acid. 
After washing in distilled water and boiling in alcohol, they can be 
examined under a low magnifying power. For imbedding, the material 
is hardened in absolute alcohol and then placed in chloroform in a closed 
glass vessel. The pieces of infected leaf remain floating on the chloro- 
form. Alcohol is then run in until the material is completely covered 
by it. After a short time the two fluids mix ; the material becomes 
impregnated, and falls to the bottom of the vessel. The saturation is 
generally completed after from four to six hours, and the pieces of leaf 
are then placed in a concentrated solution of paraffin in chloroform or 
directly in pure paraffin melting at 50° C. After sectioning, the sections 
are freed from paraffin by turpentine-oil ; then placed in absolute alco- 
hol until required for staining. 
* Oesterr. Bot. Zeitschr., xlviii. (1898) pp. 53-9, 99-105. 
t Jakrb. f. wiss. Bot. (Pfeifer u. Strasburger), xxxi. (1897) pp. 166-70. 
