56 METHODS IN PLANT HISTOLOGY 



1. Fix anthers in 1 part glacial acetic acid and 3 parts absolute alcohol from 

 12 to 24 hours. 



2. Squeeze contents of an anther into a drop of Belling's iron aceto-carmine. 

 Remove all structures except the pollen mother-cells, which must come 

 into contact with both cover and slide. Otherwise they will be washed off. 

 Place a cover glass over the drop. 



3. Heat over an alcohol flame for a second, repeating 4 or 5 times. The drop 

 must not boil. 



4. Place the slide in a Petri dish filled with 10 per cent acetic acid until the 

 cover rises from the slide. Some of the pollen mother-cells will stick to the 

 slide and some to the cover. 



5. Place both slide and cover in equal parts of absolute alcohol and acetic 

 acid. 



6. Pass through 1 part acetic acid to 3 parts absolute alcohol, 1 part acetic 

 to 9 parts absolute alcohol, absolute alcohol, equal parts absolute alcohol 

 and xylol, pure xylol, a few minutes in each. 



7. Mount in balsam. 



Dr. McClintock used certified carmine (NCa2). 



THE ANILINS 



Many of the most brilliant and beautiful stains yet discovered be- 

 long to this group. These stains are very numerous, but not so numer- 

 ous as their names; for different names have been given to the same 

 stain, and the same name has been given to different stains. For- 

 tunately, the Committee on Standardization of Biological Stains is 

 doing a good work in standardizing the nomenclature as well as the 

 stains themselves. A valuable list of synonyms, with the preferred 

 designations, was published in Science, 57:743-746, 1923, and other 

 references to the work of the commission are given in the Bibliography 

 on page 341, and brought up to 1929 in Dr. Conn's book, Biological 

 Stains. 



General formula. — Make a 10 per cent solution of anilin oil in 95 

 per cent alcohol, shaking frequently until the anilin oil is dissolved; 

 then add enough water to make the whole mixture about 20 per cent 

 alcohol; then add 1 g. of cyanin, erythrosin, safranin, gentian violet, 

 etc., to 100 c.c. of the solution. Solutions containing anilin oil do not 

 keep so well as aqueous or alcoholic solutions. Personally, we hardly 

 ever use solutions containing anilin oil. 



The anilins keep well in balsam, but not so well in glycerin. Xylol 

 is a good clearing agent for all of them; but clearing in clove oil im- 



