666 METHODS OF SPECIAL STAINING ETC. 



MiLoviDOV {Arch. Anat. Microsc, xxiv, 1928, p. 19) fixes in 

 chromic-formalin or Nemec's chromic-bichromate-formalin and 

 treats with Volkonsky's modification of Kull's method. Stain 

 in 20 per cent, acid rubin in anilin water for five minutes at 

 60 to 80° C. After cooling wash in distilled water, differentiate in 

 5 per cent, aurantia in 70 per cent, alcohol and wash quickly in 

 water. Treat for two to three minutes with a solution of 10 c.c. 

 normal caustic soda and 1 grm. phosphomolybdic acid in 90 c.c. 

 distilled water and wash quickly in water. Then stain ten to 

 fifteen minutes in a solution of 50 c.c. glycerin, 0-1 grm. potassium 

 carbonate, 0-1 grm. azur II and 0-4 grm. methylen blue in 50 c.c. 

 distilled water. Wash in water, differentiate in Unna's tannin- 

 orange, wash in water, dehydrate and mount. 



MiLoviDov (C. R. Soc. Biol., xcviii, 1928, p. 555) and Dufrenoy 

 (Stain Tech., iv, 1929, p. 13) give the following schedule : Fix in 

 a mixture of 1 per cent, chromic acid 50 c.c, 1 per cent, potassium 

 dichromate 50 c.c. and 40 per cent, neutral formalin 8 c.c, rinse 

 twenty-four hours in running water, dehydrate, imbed and cut 

 at 4jLt. Dissolve the paraffin from the slides, dip in a very thin 

 solution of collodion in absolute alcohol and ether and run through 

 the alcohols to water. Stain in anilin-acid fuchsin and wash in 

 water. Destain in aurantia in 70 per cent, alcohol and wash in 

 water. Treat for a few minutes with 1 per cent, phosphomolyb- 

 denic acid in 0-1 per cent, caustic soda, rinse and stain in Unna's 

 polychrome methylen blue. There results a very sharp differen- 

 tiation of the bacteria which are stained a deep violet blue, while 

 the mitochondria and plastids retain the red of the acid fuchsin. 



1333. Plastids. Most standard fixatives yield little or no 

 information on their structure, though some, especially of the 

 Flemming group, are suitable for studies of their form. Zimmer- 

 mann recommends a saturated solution of picric acid and corrosive 

 sublimate in absolute alcohol. Krasser (Bot. Centrbl. Hi, 1892, 

 p. 4) uses a 1 per cent, alcoholic solution of salicylic aldehyde. 

 Zimmermann recommends staining with acid fuchsin (Altmann 

 or other methods), iodine green or ammoniacal or basic fuchsin. 

 The latter two stains will not withstand dehydration through 

 alcohol and are best examined at once in glycerin. These 

 methods also suffice for pyrenoids. Zirkle {Amer. J. Bot., 

 xiii, 1926, p. 301) studied the distribution of pigments in the 

 chloroplast by means of monochromatic light of wavelengths 

 corresponding to the absorption and bright bands of the several 

 pigments. He also employed frozen sections (not below — 4° C.) 

 and chloroplasts extruded from the cell into a culture medium of 

 lactose, gelatin and glycin. 



Lowe and Lloyd {Trans. Roy. Soc. Canada, III, xxi, 1928, 

 p. 279) demonstrated the chloroplast in Hydrodictyon by the use of 

 light in the region of the absorptipn bands of chlorophyll. 



