30 PHARMACEUTICAL BOTANY 



3. Rinse sections thoroughly first in water, then in 35 per cent, 

 alcohol, then in 50 per cent, alcohol. 



4. Put them quickly through acid alcohol (i drop of HC1 in 50 

 mils of 70 per cent alcohol). 



5. Transfer to 70 per cent, alcohol for about 2 minutes. 



6. Transfer to 85 per cent, alcohol for about 2 minutes. 



7. Transfer to 95 per cent, alcohol for about 2 minutes. 



8. Transfer to absolute alcohol for about 2 minutes. 



9. Clear sections in a mixture of equal parts of cedar oil and phenol 

 for at least 2 minutes. 



10. Remove excess of clearing solution and mount in balsam. 



11. Label slide. 



DESILICIFICATION OF HARD WOODY MATERIALS 



It frequently happens, even after prolonged maceration or boiling 

 in alkaline solutions, that thin sections of hard roots, stems, woods or 

 fruits are difficult or impossible to procure. This is due to the pres- 

 ence of deposits of silica and other mineral substances that usually 

 occur in woody tissues. Therefore, it is of prime importance that 

 these substances be removed as thoroughly as possible. For this 

 purpose a 10 per cent, aqueous solution of commercial Hydrofluoric 

 Acid (or stronger solutions up to the pure acid for very hard ma- 

 terials) is most useful. Small fruits or short segments of other hard 

 materials are placed in this acid (which should be kept in a bottle 

 coated internally with a thick layer of paraffine) for from 3 days to a 

 week, depending on the size of the objects, with one or two changes 

 of the acid. The acid is then washed out thoroughly with running 

 water for 2 to 5 hours. This treatment completely frees the tissues 

 of all mineral deposits without affecting the organic structure. 



SCHULZE'S MACERATION PROCESS 



This method is employed for the separation of cells. Radial- 

 longitudinal sections, that may be cut with a pen knife, are placed in 

 a beaker or test tube containing 50 mils of nitric acid of specific 

 gravity 1.3 (about 2 volumes of nitric acid and i volume of water 

 will serve purpose). To this add i gram of chlorate of potash 

 crystals and heat gently until the reddish color which first appears 



