36 Methods in Plant Histology 



than xylol. When the absolute alcohol has deteriorated so that xylol 

 no longer clears the sections, clove oil may still clear with ease. 

 While clove oil will clear from 95 per cent alcohol, it is better to use 

 absolute. Since preparations cleared in clove oil harden slowly, it is 

 a good plan to treat them with xylol before mounting in balsam. 

 Gentian-violet is somewhat soluble in clove oil, and this fact makes 

 it possible to secure a beautiful differentiation, because the stain 

 is extracted from some elements more rapidly than from others. 

 The stain may be extracted completely from the chromosomes 

 during the metaphase and still remain bright in the achromatic- 

 structures. After the desired differentiation has been attained, the 

 preparation should be placed in xylol to remove the clove oil, since 

 the continued action of the clove oil would cause the preparation to 

 fade. Do not use a Slender dish for clove oil, but keep it in a 50 c.c. 

 bottle. Put on a few drops, and immediately drain them off in such 

 a way as to remove the alcohol as completely as possible. Then 

 flood the slide and pour the clove oil back into the bottle, repeating 

 the process until the proper differentiation has been reached. Re- 

 place the clove oil with xylol and mount in balsam. With stains 

 not soluble in clove oil, the xylol is not necessary, except to facilitate 

 the hardening of the preparation. 



Clove oil is used in removing the celloidin matrix from celloidin 

 sections. It is useless as an agent to precede infiltration with paraffin. 



Eycleshymer's Clearing Fluid.- -This is a mixture of equal parts 

 of bergamot oil, cedar oil, and carbolic acid. It clears readily from 

 95 per cent alcohol, and consequently is useful in clearing celloidin 

 sections when it is desirable to preserve the celloidin matrix. In 

 sections stained with haematoxylin, or haematoxylin. and eosin, the 

 stain may be removed completely from the matrix by the use of 

 acid alcohol, and the matrix may be preserved by clearing from 95 

 per cent alcohol. 



It is not intended that the mixture should be used to precede 

 infiltration with paraffin. 



Other Clearing Agents. Bergamot oil, carbolic acid, turpentine, 

 benzine, gasoline, and other reagents have been tried for clearing, 

 but none seem to be worth more than a warning mention. 



