34 
METHODS IN PLANT HISTOLOGY 
15 per cent alcohol is too strong for a beginning. It is maintained 
that, in addition to the damage done by transferring from water to 
so strong an alcohol, the final dehydration is not so perfect as it is 
when the series begins with a weaker alcohol. Yamanouchi, whose 
work upon delicate algae has been particularly successful, uses the 
following series: 2J, 5, 7§, 10, 15, 20, 30, 40, 50, 70, 85, 95, and 
100 per cent. After such gradual early stages, there seems to be no 
objection to the less gradual stages which follow. Of course, there 
is no particular virtue in the fractions: it is convenient to make a 
10 per cent alcohol, then dilute it one-half for the 5 per cent, and dilute 
the 5 per cent one-half for the 2| per cent. The 7| per cent is made 
with sufficient accuracy by adding a little water to the 10 per cent 
alcohol. For each of the grades up to 50 per cent, one hour is enough 
for objects like fern p^othallia; but an hour and a half should be 
given to each of the remaining grades. Objects like onion root-tips 
should have 2 hours in each of the grades up to 50 per cent, and 3 hours 
in each of the others. Quarter-inch cubes should have 3 or 4 
hours in each grade up to 50 per cent, and 4 or 5 hours in the others. 
The times for larger objects will be longer and will depend upon the 
size and density. In all cases, the absolute alcohol should be changed 
2 or 3 times. The grades below 100 per cent can be used repeatedly. 
The absolute alcohol should not be used again for this purpose, but 
may be put back into the 95 per cent bottle. It is always well to 
filter the alcohols when pouring back into the bottle. Otherwise, 
there would soon be an accumulation of starch grains, pollen grains, 
spores, and various other things. Waste alcohol as strong as 85 or 
95 per cent will be useful for rinsing one’s hands when dealing with 
Venetian turpentine. If it is necessary to be very economical, the 
stronger alcohols may be filtered into a single large bottle and the 
strength of the mixture can then be determined by using an alcohol¬ 
ometer. Knowing the strength of the mixture, one can easily make 
any weaker grade. 
Be very sure that the bottles or Stenders for absolute alcohol 
are perfectly dry; also, keep the bottles well corked and keep 
the lids on the Stenders. The importance of excluding moisture 
cannot be exaggerated. Tightly fitting corks and closely fitting 
covers are better than absorbents; prevention is better than 
cure. 
The lower grades are made up from 95 per cent alcohol. 
