BRIEFER ARTICLES 



SECTIONING HARD WOODY TISSUES 



In preparing hard or refractory woods for sectioning it has been 

 customary to soften in hydrofluoric acid and imbed in either celloidin or 

 gelatin, the latter process being favored in the sectioning of partly 

 disorganized material. In connection with certain anatomical prob- 

 lems, a method of imbedding in paraffin after the demineralization of 

 the woody tissues by means of hydrofluoric acid has been developed, 

 and has proved most successful in dealing with either hard woody 

 tissues or non-homogeneous objects, possessing both soft delicate 

 tissues and hard lignified structures. More uniform results are assured 

 with this method, and it is also possible thus to secure an unbroken 

 series of sections without the tedious and complicated process involved 

 in the celloidin method. 



Preparation or material. — The woody material is first cut into 

 blocks of a convenient size for sectioning. In the case of hard stems 

 and roots a fine sharp hacksaw should be used to prevent the tearing 

 or jamming of the tissues in the vicinity of the cut surfaces. More 

 delicate material, such as small roots, seedlings, herbaceous stems, 

 etc., may be cut into smaller portions by means of a sharp knife, pref- 

 erably a Gillette razor blade. If the material to be examined is dead 

 and dry, it should be repeatedly boiled in water and cooled to remove 

 all air from the tissues, as in the celloidin method. If living, it should 

 be well fixed in some suitable reagent. A mixture of formalin, alcohol, 

 and glacial acetic acid has proven satisfactory for most anatomical 

 work: 50 per cent alcohol, 100 cc; formalin (commercial) , 6 cc; glacial 

 acetic acid, 3 cc. Fix 24-48 hours and rinse thoroughly in running water. 



Demineralization. — The blocks of material thus prepared are 

 ready for the next step in the process, which is the demineralization 

 and general softening of the lignified structures of the stem by means 

 of hydrofluoric acid. The blocks are transferred directly from water 

 to either 50 per cent aqueous solution of commercial hydrofluoric acid 

 or hydrofluoric acid full strength. The strength of the acid and the 

 length of time in the reagent depend, of course, upon the nature of the 

 material. Cubes of very hard woods of a comparatively homogeneous 

 structure, such as the oak, require 3-4 weeks in 50 per cent hydrofluoric 



Botanical Gazette, vol. 70] 



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