SOME SPECIAL METHODS 649 



p. 154) uses a 10 per cent, gelatin solution. See also Ohga, Hot. 

 Mag. Tokyo, xl, 1926, p. 550. 



1286 his. Preservation of Natural, especially Green, Colour. The 



simplest fluid consists of concentrated formalin saturated with 

 copper acetate, diluted to 4 per cent, for use. This is especially 

 useful for Chlorophycese and Myxophycea?. The green colour is 

 more bluish than the original and there is usually some shrinkage. 

 Semichon {Rev. Path. Veg. et Ent. Agric, xiv, 1927, p. 228) 

 suggests water 8 c.c, 40 per cent, formalin 1 c.c, 4 per cent, 

 aqueous solution of copper acetate 1 c.c. Evans {Journ. Quekett 

 Micr. Club., xiv, 1921, p. 225) suggests fixation in a mixture of 

 10 c.c. of 5 per cent, neutral formalin and 1 c.c. of 10 per cent, 

 zinc acetate in thymol water, diluted if shrinkage occurs. After 

 a time the material is washed and preserved in glycerin by con- 

 centration. Keefe {Science, Ixiv, 1926, p. 331) gives ; 



Fifty per cent, alcohol . . . .90 c.c. 



Commercial formalin . . . . 5 „ 



Glycerin ...... 2-5 „ 



Glacial acetic acid .... 2-5 ,, 



Copper chloride . . . . .10 grm. 



Uranium nitrate . . . . 1-5 ,, 



This acts as a fixing and preserving fluid, causes little or no 

 shrinkage and gives a natural green colour. For Myxophycese, 

 substitute 10 grm. copper acetate for the copper chloride and 

 uranium nitrate. For yellowish-green plants reduce the copper 

 chloride to half. Delicate forms are fixed in forty-eight hours, 

 others in three to ten days. In making microscopic mounts 

 transfer to a mixture from which the alcohol has been omitted. 



JiROUCH {Stain Tech., iv, 1929, p. 17) fixes plant tissue at least 

 forty-eight hours in Keefe's fluid. Wash well in water. Steep in 

 20 per cent, gum arable for one to two days and cut after freezing 

 when the mass has just started to melt. Stain lightly in 

 Delafield's ha^matoxylin (5 per cent, for about two minutes). Blue 

 in distilled water containing a little sodium carbonate. Dehydrate 

 in glycerin and mount in glycerin jelly. 



Neumayer {Ber. Deut. hot. Ges., xl, 1922, p. 41) fixes fronds of 

 Angiopteris in hot concentrated potassium bichromate solution. 

 The green colour of the chloroplasts is retained after dehydrating, 

 imbedding and mounting in the usual way. 



See also Maltby, Mus. Journ., :kxv, 1926, p. 329 ; Seif-el- 

 Nasr, Min. Agr. Egypt., Tech. and Sci. Serv. Bull., cxxiv, 1932, 

 p. 1 ; NiEUWLAND and Slavin, Proc. Indiana Acad. Sci., xxxviii, 

 1929, p. 103 (preservation of Monotropa, etc., without discolora- 

 tion). 



