﻿igi6] BRIEFER ARTICLES 255 



A METHOD FOR THE DEHYDRATION OF HISTOLOGICAL 

 MATERIAL 



A combination of the glycerine dehydration method with the paraffin 

 imbedding method in preparing histological material has given such 

 satisfactory results that, while there is nothing new in the method itself, 

 its advantages seem to justify bringing it to the attention of botanists, 

 since the combination of the two is not in general practice. For some 

 time the writer has been using glycerine in dehydration instead of alco- 

 hol in the preparation of small objects such as the megaspores and micro- 

 spores of Marsilia and Selaginella, and has recently attempted using it 

 on larger objects such as leaf tissue, ovulate and staminate sporophylls 

 of the conifers, and anatomical material generally. It has uniformly 

 given good results and indicates possibilities of more general application. 



The method is exactly the same as is given for the glycerine dehydra- 

 tion in the preparation of glycerine and Venetian turpentine mounts of 

 algae and fungi. The material to be imbedded is first killed with some of 

 the usual killing agents, such as Fleming's solution or chromo-acetic acid 

 solution 1 : 1 : 100 diluted to one-third or one-fourth strength at a temper- 

 ature of 5o-6o°C. After killing for 12-24 hours the usual washing with 

 water should follow. When free from acid the material is placed in a 

 shallow open container, as a watch glass or a Petri dish, and covered with 

 a ro per cent glycerine solution in sufficient quantity to more than cover 

 the material. The dish is allowed to stand open, but protected from the 

 dust and subjected to the ordinary evaporation of the laboratory air, 

 insuring a steady rapid dehydration by the evaporating of the water 

 from the glycerine solution which gradually becomes concentrated. 

 Within two or three days the glycerine is fully concentrated and the 

 material is at about the same stage of concentration it would have been 

 had it been "run up" through grades of alcohol to about 95 per cent. 



The glycerine should be rather carefully removed by washing the 

 material in 95 per cent alcohol. Specific manipulation for this particular 

 process may be devised for each kind of material. Large pieces of 

 material may often be removed from the glycerine with forceps or needles, 

 or frequently the glycerine may be poured off the material. In any 

 event, it is important to remove all of the glycerine by repeated washings 

 in 95 per cent alcohol, since the presence of the former seems to interfere 

 in the further processes of imbedding. Absolute alcohol is used to 

 complete the dehydration, and any of the standard methods of substitu- 

 ting a paraffin solvent for the alcohol may follow from this point. 



The advantages of the method are as follows: (1) dehydration is 

 accomplished uniformly, rapidly, and with a minimum of work and 



