624 BOTANICAL TECHNIQUE 



HoRTON {Ann. Bot., xxxviii, 1924, p. 404) finds that prolonged 

 treatment with diUite sodium hypochlorite solution brings 

 material, particularly of flowers, into a surprisingly good condition. 



1240. Dehydration. Conduct with regard to the nature of 

 material, its bulk and the purpose (anatomical or cytological) to 

 which it is to be put. Anatomical inaterial of a more resistant 

 nature, after washing, may be passed through 15, 25, 50, 70, 



95 per cent, alcohols to absolute with three to six hours in each 

 grade. More delicate material requires an extended series with 

 10 per cent, intervals between grades, and one to two or more 

 hours in each. Cytological material and very delicate algal and 

 fungal inaterial may need closer grades, especially in the lower 

 and upper jmrts of the series, viz., 2^, 5, 10, 15, 20, 25, 30, then 

 by 10 per cent, intervals to 90, 95, and 100 per cent., with one to 

 two hours or more in each. 



According to Kisser {Zeit. wiss. Mik., xlvi, 1929, p. 269), 

 the use of absolute alcohol is unnecessary. Transfer from 95 or 



96 per cent, alcohol through mixtures of alcohol and xylol to 

 xylol ; imbed in paraffin or mount in balsam. Mixtures of 

 alcohol and benzene may be used, and in fact are preferable as 

 water is more soluble in benzene than xylene. 



Hartridge {Journ. Physiol., liv, 1920, p. 8) recommends amyl 

 alcohol, in place of absolute alcohol and clove oil, following 95 

 per cent, alcohol and followed by Canada balsam in xylol ; and 

 also for passing to No. 1 petrol for paraffin imbedding {q.v.). 



Sass {Stain Tech., vii, 1932, p. 65), McFarland {Science, Ivi, 

 1922, p. 43), and Lyon {Science, Ivii, 1923, p. 644), use acetone in 

 place of alcohol. 



See also Hill, Bot. Gaz., Ixi, 1916, p. 255 (glycerin dehydra- 

 tion) ; Bradbury, Science, Ixxiv, 1931, p. 225 (isopropyl alcohol) ; 

 Courtney, Science, Ixvii, 1928, p. 225. 



Marine plant material, fixed in solutions compounded of sea- 

 water, are to be brought in to fresh water before dehydration, 

 Dehyhration without shrinkage or the production of cloudiness can 

 usually be effected by passing through the following mixtures : — 



and thereafter through mixtures of fresh water and alcohol only. 

 Filamentous and imicellular organisms are often best dehydrated 

 by placing them in 5 per cent, aqueous glycerin and allowing this 

 to concentrate, not too rapidly (at least two days), in a place 

 protected from dust. Later replace the concentrate with 95 per 

 cent, or absolute alcohol. See Hemenway, Science, Ixxii, 1930, 

 p. 251. 



Dilute (10 per cent.) aqueous phenol can also be used and 



