FORMULAS FOR REAGENTS 389 



Zenker's fluid. — 



Corrosive sublimate 5 g. 



Glacial acetic acid 5 c.c. 



Potassium dichromatc 2 g. 



Distilled water 100 c.c. 



Fix 12-24 hours or even a couple of days. Wash in water and add 

 iodine, as in all reagents containing mercury. This is good for embryo 

 sacs and for free nuclear stages in endosperm of gymnosperms and 

 angiosperms. 



Bensley's formula (for chondriosomes). — 



2^ per cent corrosive sublimate in water 4 parts 



2 per cent osmic acid 1 part 



Yamanouchi's formula (for chondriosomes). — 



Neutral formalin 10 c.c. 



Water 90 c.c. 



Gilson's fluid. — 



95 per cent alcohol 42 c.c. 



Water 60 c.c. 



Glacial acetic acid 18 c.c. 



Concentrated nitric acid 2 c.c. 



Corrosive sublimate (saturated solution in water) 11 c.c. 



Bensley's formula (for canal system). — 



1. Bichromate of potash 2| g. 



2. Corrosive sublimate 5 g. 



3. Water 90 c.c. 



4. Formalin (neutral) 10 c.c. 



Make a solution of 1, 2, 3, and then add the neutral formahn. 



Osmic acid (stock solution). — 



Osmic acid . 1 c.c. 



Distilled water 1 c.c. 



The bottle in which the solution is to be kept, and also the glass tube 

 in which the acid is sold, must be thoroughly cleaned. Break off the 

 end of the tube, and drop both tube and acid into the distilled water, 

 or simply drop the tube into the bottle and shake the bottle until the 

 tube breaks. 



Unicellular forms in a drop of water, inverted over the neck of the 

 bottle, fix in 2-5 seconds. 



