632 BOTANICAL TECHNIQUE 



put them into equal parts of 95 per cent, alcohol and glycerin 

 for a week or more. Very hard woods may also need treatment 

 with hydrofluoric acid ; a 25 per cent, solution for a week, 

 followed by washing and steeping in alcohol glycerin, should 

 suffice. 



Evans and Cro^\tell {Stain Tech., v, 1930, p. 149) have 

 described a similar method. Water is boiled slowly in an 

 Erlenmeyer flask from which the vapour is led to the microtome 

 through a small copper tube in which there are a few coils. A 

 Bunsen burner beneath the coils vaporises the water before it 

 leaves the tube. The steam flows over the piece of wood to be 

 sectioned. The authors have cut up to 500 sections of very hard 

 wood with a single sharpening of the razor. They also suggest a 

 possible imj^rovement, which consists in using tubing of alu- 

 minium or monel metal instead of copper. 



1257. Larbaud's Butyl Alcohol Method (C. R. Acad. Sci., 

 Paris, clxxii, 1921, p. 1317). Butyl alcohol softens wood and 

 permits smooth sectioning of material that would otherwise be 

 brittle and difficult to cut. It can be used for dehydration and 

 clearing. See § 127. 



Zirkle's schedule {Science, Ixxi, 1930, p. 103) permits more 

 gradual dehydration than Larbaud's method. 



Stage . .123456789 10 11 



Water . . 95 89 82 70 50 30 15 5 



Ethyl alcohol . 5 11 18 30 40 50 50 40 25 



Butyl alcohol . 10 20 35 55 75 100 100 



Leave one hour in each stage, over night at stage 6. Leave 

 some time in pure butyl alcohol, so that all the water is extracted. 

 Two-thirds fill a vial with paraffin. Let the paraffin harden and 

 place the material on it, cover the specimens with butyl alcohol 

 and place in a paraffin oven. As the paraffin melts the material 

 sinks and comes into contact with almost pure paraffin ; the butyl 

 alcohol remains floating on the top. Two changes of paraffin are 

 sufficient, the length of time in each depending upon the size of 

 the specimens. Slight traces of butyl alcohol in the paraffin 

 blocks do not render them crumbly, as does xylol. 



Butyl alcohol does not soften wood which has been hardened 

 by fixation, by drying or by too rapid dehydration. The method 

 is also excellent for delicate materials. 



ZiRKLE {ibid.) has also used Painter's method {Anat. Rec, 

 xxvii, 1924, p. 77), in which anilin oil replaces the higher con- 

 centrations of alcohol. Replace the anilin oil with methyl 

 salicylate (oil of wintergreen) and pass from the latter into 

 paraffin. 



1258. Sectioning of Cotton and other Fibres. Denham {Nature, 

 cvii, 1921, p. 299) uses a modification of Breckner's method 



