PLANT CHROMOSOMES G77 



Catcheside {Genetica, xvii, 1935, p. 313) uses uranium trioxide 

 in place of osmium tctroxide in the standard formulae. Material 

 then requires bleaching with hydrogen peroxide (1 part to 4 parts 

 of 80 per cent, alcohol) or with nascent chlorine. Subsequently 

 mordant with 1 per cent, aqueous chromic acid before staining, 

 or use La Cour's gentian violet-iodine-chromic acid technique. 

 See also Nebel {Zeits. Zellf. mikr. Anat., xvi, 1932, p. 251). 



1357. S. Na Yashin's {Mem. Soc. Nat. Kiev., 1912, p. 28) Fixative 

 is a Flemming formula in which the osmic acid is replaced by an 

 equal volume of 40 per cent, formalin. He used 15 parts of 1 per 

 cent, chromic acid, 4 parts of 40 per cent, formalin and 1 part of 

 glacial acetic acid. In a formula now commonly used the chromic 

 acid is reduced to 10 parts. For an analysis of the fixing action, 

 see Levitsky, Bull. Appl. Bot. Gen. and Plant Breed., xxvii, 1931, 

 p. 175. 



The principal modifications are : Karpechenko [J. Genet., xiv, 

 1924, p. 387), 1 per cent, chromic acid, 15 parts ; glacial acetic 

 acid, 1 part ; 16 per cent, formalin, 3 parts ; distilled water, 17 

 parts. 



Belling's {The Use of the Microscope, p. 234) : 



Solution A : chromic acid crystals, 5 grm. ; glacial acetic acid, 

 50 c.c. ; distilled water, 320 c.c. 



Solution Bl (for prophase stages) : commercial formalin, 

 200 c.c. ; distilled water, 175 c.c. 



Solution B2 (for metaphase stages) : commercial formalin, 

 100 c.c. ; distilled water, 275 c.c. 



For use, take equal parts of solutions A and either Bl or B2, 

 according to the stage of meiosis being fixed ; the stage is pre- 

 determined by examination of one anther or part of an anther 

 in a drop of iron aceto-carmine. Always use the mixture freshly 

 prepared ; it deteriorates rapidly. Fix three hours ; a longer 

 period {e.g., twelve hours) is not injurious. Transfer slides to a 

 dish containing solution A only for ten minutes ; a longer stay is 

 injurious. Remove anther fragments and debris. Rinse in water. 

 Pass slides through 15, 30 and 50 per cent, alcohols (five minutes 

 each), into 70 per cent, alcohol and leave overnight. 



Weber {Univ. Calif. Pub. Bot., xi, 1930, p. 319). 



Mix equal parts of solutions A and B. 



Solution A : glacial acetic acid, 10 c.c. ; chromic acid, 1 grm. ; 

 water, 65 c.c. 



Solution B : formalin, 40 c.c. ; water, 35 c.c. 



Randolph {Stain Tech., x, 1935, p. 95) uses equal parts of solu- 

 tions A and B in : 



Solution A : CrOg (chromic anhydride), 1 grm. ; glacial acetic 

 acid, 7 c.c. ; distilled water, 92 c.c. 



Solution B : neutral formalin, 30 c.c. ; distilled water, 70 c.c. 



Fix (root-tips) twelve to twenty-four hours and then transfer 



