56 Methods in Plant Histology 



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 

 repeatedly 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 v 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 reel 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 



