26 Methods in Plant Histology 



immediately fill the Stender full of 30 per cent alcohol and thus 

 dissolve the fumes in alcohol. This will bleach sections in 10 minutes, 

 or even less. Wash in 30 per cent alcohol 2 or 3 hours before stain- 

 ing. Trondle uses 1 per cent chromic acid in water for bleaching; 

 it is slow, requiring about 8 hours, but he maintains that material 

 stains better than after bleaching with peroxide of hydrogen. 

 According to Miss Merriman, the linin in the nuclei of onion root- 

 tips is not so well preserved in this solution, but the arrangement of 

 the chromatin granules is brought out with greater distinctness. 

 Flemming's safranin, gentian-violet, orange combination gives excel- 

 lent results after this reagent. 



d) Flemming's Fluid (weaker solution). 



f 1 per cent chromic acid 25 c.c. 



A \ 1 per cent acetic acid 10 c.c. 



I Water 55 c.c. 



B. 1 per cent osmic acid 10 c.c. 



As in case of the stronger solution, mix A and B only as needed for 

 immediate use. 



Many prefer the weaker solution, because the blackening is not 

 so extreme and material does not become quite so brittle. Some 

 allow the solution to act for an hour and then transfer the material to 

 solution A for about 24 hours. This secures the rapid killing, 

 which is the principal virtue of the osmic acid, and avoids the dis- 

 agreeable blackening, so that little or no bleaching may be necessary. 



e) Benda's Fluid.- 



1 per cent chromic acid 16 c.c. 



2 per cent osmic acid 4 c.c. 



Glacial acetic acid 2 drops 



This modification of Flemming's stronger solution has been used 

 very successfully in recent investigations upon chromatin. 



/) MerkePs Fluid. 



Equal volumes of a 1 . 4 per cent solution of chromic acid and a 

 1 .4 per cent solution of platinic chloride. This is also an expensive 

 reagent. It is recommended for mitotic phenomena, but does not 

 seem to equal Flemming's solution. 



