CHAPTER XI 
THE CELLULOSE ACETATE METHOD 
We believe that the cellulose acetate method is destined to 
prove as successful with hard woody tissues as the Venetian turpentine 
method has proved with unicellular and filamentous forms; but, it 
must be confessed that investigators have been unsuccessful in their 
experience with cellulose acetate. Nevertheless, refractory material, 
like oak and even harder woods, has yielded thin transverse sections. 
Cellulose acetate does not injure the finer details of structure, and, 
on that account, will be superior to hydrofluoric acid, when students 
have solved the present uncertainties in regard to it. We have such 
confidence in the value of the method that we are quoting, in full, 
Mrs. Williamson’s short account in the Annals of Botany for January, 
1921, which is the only published information upon the subject: 
A NEW METHOD OF PREPARING SECTIONS OF HARD 
VEGETABLE STRUCTURES 
In order to prepare sections of hard vegetable structures it is essential 
that some method should be devised by which the structure is not only 
embedded but softened, so that sections can be cut easily and smoothly. 
After various methods had been tried, the cellulose acetate method success¬ 
fully used by Dr. Kernot for embedding and sectioning the fabric of aeroplane 
wings was used. It was discovered that this method not only embedded 
hard vegetable structures, but also softened them so that sections are easily 
obtained. It proved best to use cellulose acetate of French manufacture 
made from pure cellulose, as the viscosity is more uniform than that of 
English manufacture, which is obtained from the cellulose of wood. 
In the preliminary experiments pieces of oak and beech, cut into half¬ 
inch cubes, were passed through strengths of alcohol, then placed in pure 
acetone for two hours and finally into a 12 per cent solution of cellulose 
acetate in acetone. There they were left for two months and excellent 
sections were obtained. Further experiments showed that the passage 
through alcohols was unnecessary. In the final experiments the pieces of 
wood were placed in water and the air removed from them, after which they 
were put into pure acetone for 1 to 2 hours and finally into the solution of 
cellulose acetate. It was found that the length of time of immersion in the 
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