60 
METHODS IN PLANT HISTOLOGY 
the alcohol: then transfer directly from water to 95 per cent alcohol, 
allowing the alcohol to act for only 2 or 3 seconds, then allow the 
absolute alcohol to act for 5 or 6 seconds, and then, while the stain 
is still coming out in streams, begin the treatment with clove oil. 
Holding the slide in one hand, pour on a few drops of clove oil, 
and immediately drain off in such a way as to carry off the alcohol. 
This clove oil should not be used again. Then flood the slide repeat¬ 
edly with clove oil, pouring the clove oil back into the bottle. A 
50-c.c. bottle of clove oil is large enough. About 100 mounts can 
be cleared with 50 c.c. of this oil. The clove oil is a solvent of 
gentian-violet, but it dissolves the stain from some structures more 
rapidly than from others; e.g., the stain may be completely removed 
from the chromosomes while it is still bright in the achromatic 
structures. As soon as the stain is just right, drain off the clove oil 
and leave the slide in xylol for a minute or two before mounting in 
balsam. This is a necessary step, because the continued action of 
clove oil would cause the preparation to fade. As may be inferred 
from what has preceded, alcohol would soon extract the stain, without 
any application of clove oil. The clove oil is used, not only because 
it extracts the stain more slowly, but because it dissolves the stain 
from some structures more rapidly than from others; e.g., the 
stain may be completely removed from the chromosomes while it 
is still bright in the achromatic structures, so that with safranin 
and gentian-violet one can get red chromosomes on a violet 
spindle. 
Some still use cedar oil to follow the clove oil. This stops the 
action of the clove oil, but the preparations harden slowly. 
Gentian-violet is an excellent stain for achromatic structures in 
all stages of development. Chromatin, in many of its stages, is 
also stained. In metaphase and anaphase one should be able to 
get red chromosomes and violet spindles with safranin and gentian- 
violet. If the chromosomes also persist in retaining the violet, 
shorten the stain in gentian-violet. Cilia stain well; starch grains 
stain deeply, chromatophores less deeply, and lignified walls may 
not stain at all. One should be able to get red lignified walls and 
violet cellulose walls with safranin and gentian-violet. 
Cyanin.—This stain is also called Quinolein blue and Chinolin 
blue. Dissolve 1 g. of cyanin in 100 c.c. of 95 per cent alcohol and 
add 100 c.c. of water. The cyanin would not dissolve in 50 per cent 
