660 METHODS OF SPECIAL STAINING ETC. 



vital stains. Becker (Ada Soc. Bot. Polonice vi, 1929, p. 214) 

 found solutions of neutral red, at dilutions of 1 : 20,000 to 

 1 : 15,000, did not disturb the course of mitosis in Stratiotes, 

 Hydrocharis and Nuphar. Compare also Becker, Cytologin iv,, 

 1933, p. 135, where it is shown that the appearance of abnormal 

 mitoses depends upon the concentration and length of exposure 

 to the dye. Guilliermond {Bull. Hist. Appl. Physiol, et Path., 

 iv, 1927, p. 125) finds that it stains only the contents of the 

 vacuome and does not modify the structure. Hitchcock [Bull. 

 Torrey Bot. Club, xlvi, 1919, p. 375) finds a differential staining 

 of the cytoplasm of Characeae by neutral red. Guilliermond has 

 also made considerable use of Janus green B. 



KiJSTER {Ber. Oberhessisch. Ges. Natur.-u. Heilkunde. Naturwiss., 

 xi, 1927, p. 8) found bromo-phenol blue (cells coloured blue) and 

 phenol red (cells coloured a deep yellow) were pH indicators 

 unusually harmless to cells of the epidermis of Allium bulb-scales. 

 He also found malachite green a vital stain in 0-1 per cent, solution. 

 According to Albach {Zeits. Wiss. Mikr., xliv,, 1927, p. 333 ; 

 Protoplasma v, 1928, p. 410) such a solution gives a clear vital 

 stain in one minute ; a 0-001 per cent, solution requires a longer 

 time, but in it the epidermal cells remain alive forty-eight hours. 

 Albach states that methyl green is also a vital stain. Paltaup' 

 {Sitzungsber. Akad. Wiss. Wien Math.-Naturw. KL, Abt. I, 

 cxxxvii, 1928, p. 691) finds erythrosin, eosin and dahlia violet stain 

 the living nuclei of several tissues. The cell sap is not stained. 

 The colour is always diffuse, and is greatly aided by nitrates of K, 

 Mg, Ca and Na, Al2(S04)3, alcohol, ether and high temperature, 

 but not by light. Dahlia violet stains well without the addition 

 of salts. Chrysoidin and water blue stain the cytoplasm, but not 

 the nucleus. Isotonic solutions of neutral red, methylen blue or 

 brilliant cresyl blue deeply stain the vacuolar material of living 

 tissues ; the reaction in many cases is apparently due to the 

 presence of phenolic compounds. 



See also Bailey and Zirkle, J. Gen. Phys., xiv, 1931 ; 

 Sherwood, Proc. Exp. Biol. Med., xxiii, 1926, p. 622. 



1324. Direct staining is frequently used on material without 

 previous fixing and mordanting processes. The dyes are usually 

 highly toxic. Iodine, eosin, picro-nigrosin, aceto-methyl green 

 (see § 363) and aceto-carmine are most useful. Stain five minutes 

 in 1 per cent, aqueous eosin, differentiate in water and fix the 

 stain with 2 per cent, aqueous acetic acid. The material can be 

 treated with aqueous iodine solution first to stain the starch and 

 afterwards stained with eosin. 



1325. Plasmodesmen (protoplasmic connections) are generally 

 made more evident by swelling of the cell-walls. Swell with 

 25 per cent., or stronger, sulphuric acid to which iodine has been 

 added. Or fix with 1 per cent, osmic acid and stain with crystal 



