Notes. 
i39 
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 successfully used by Dr. Kernot 
for embedding and sectioning the fabric of aeroplane wings was used. It was dis- 
covered 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 in 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 obtained. Further experiments showed 
that passage through alcohol 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 solution of cellulose acetate 
necessary for softening the tissues varied with the hardness of the wood ; the minimum 
time for soft woods being two days ; for woods such as oak and beech at least six 
days are required. Experiments were tried with sal ( Shorea robusta) and Pyingadu 
(Xylia dolabriformis), one of the Indian ironwoods, which is extremely hard. After 
fourteen days in the cellulose acetate solution it was possible to obtain transverse 
sections of these hard woods. The cellulose acetate solution is therefore capable of 
softening even the hardest wood in a relatively short time. 
In order to stain sections — either hand or microtome — obtained by this method, 
it is necessary to wash them in pure acetone for 1 to 2 minutes to remove the cellulose 
acetate, wash in alcohol 1 to 2 minutes, and pass on to the stains selected. Various 
staining methods for cell-walls — such as aniline chloride, methylene blue, and Congo 
red, ammoniacal fuchsin and Kleinenberg’s haematoxylin, &c. — were tried with 
success. A comparison with stained sections of untreated wood revealed no differences. 
Delicate tissues in the wood and hyphae of fungi infecting the wood also stain well 
and are unaffected by the treatment. 
A satisfactory method of preparing sections of hard vegetable structures is therefore 
supplied by the use of a 12 per cent, solution of cellulose acetate in pure acetone for 
softening and embedding. 
H. S. WILLIAMSON. 
Imperial College of Science and Technology. 
