HOW TO USE THE MICROSCOPE 



29 



thin, flexible part of a plant, it may be placed between pieces 

 of elder pith or slices of carrot or potato before cutting. 



SHORT PARAFFIN PROCESS 



In most cases, however, more perfect sections will be ob- 

 tained if the specimens are embedded in paraffin, by the quick 

 paraffin process, which is easily carried out. 



After boiling the specimen in water, remove the excess of 

 moisture from the outer surface with filter paper or wait until 

 the water has evaporated. Next make a mould of stiff card- 

 board and pour melted paraffin (melting at 50 or 60 degrees) 

 into the mould to a height of about one-half inch, when the 

 paraffin has solidified. This may be hastened by floating it 

 on cool or iced water instead of allowing it to cool at room 

 temperature. 



The specimens to be cut are now placed on the paraffin, 

 with glue, if necessary, to hold them in position, and melted 

 paraffin poured over the specimens until they are covered to a 

 depth of about one-fourth of an inch. Cool on iced water, 

 trim off the outer paraffin to the desired depth, and the speci- 

 men will be in a condition suitable for cutting. 



Good workable sections may be cut from specimens embedded 

 by this quick paraffin method. After a little practice the entire 

 process can be carried out in less than an hour. This method 

 of preparing specimens for cutting will meet every need of the 

 pharmacognosist. 



LONG PARAFFIN PROCESS 



In order to bring out the structure of the protoplast (living 

 part of the cell), it will be necessary to begin with the living 

 part of the plant and to use the long paraffin method or the 

 collodion method. 



Small fragments of a leaf, stem, or root-tip are placed in 

 chromic-acid solution, acetic alcohol, picric acid, chromacetic 

 acid, alcohol, etc., depending upon the nature of the specimen 

 under observation. The object of placing the living specimen 

 in such solutions is to kill the protoplast suddenly so that the 

 parts of the cell will bear the same relationship to each other 



