CHAPTER VIII 

 THE VENETIAN TURPENTINE METHOD 



Twenty years ago Pfeiffer and Wellheim 1 described a method for 

 mounting fresh-water algae in Venetian turpentine. The method 

 received no recognition in the United States and did not become 

 current in Europe. I made a casual trial of the method when pre- 

 paring the first edition of this book, but the preparations were such 

 miserable failures that the process did not seem worth mentioning. 

 The method was next brought to my attention during a demonstration 

 in Strasburger's laboratory at Bonn. He was using preparations of 

 Zygnema and Spirogyra, the staining of which surpassed anything I 

 had ever seen. He remarked that it was not worth while to consult 

 the lengthy article, because his preparations had been made by 

 the authors and no one else had made a success of the method. How- 

 ever, when I returned, I made a careful study of the process, and 

 finally learned to use it successfully. The details as given in this 

 paper were too indefinite for practical use, but, after one has learned 

 the method, the article can be read with profit. 



The great practical advantages of the method are that prepara- 

 tions are as hard and durable as balsam mounts, and that a much 

 greater variety of staining is possible than in case of glycerin mounts. 



After fixing and washing in water, the general outline of the 

 method is as follows: 



1. 10 per cent glycerin until concentrated. 



2. Wash the glycerin out thoroughly in 95 per cent alcohol. 



3. Stain. Use stains dissolved in about 90 per cent alcohol. 



4. Wash in 95 per cent alcohol, and complete the dehydration in 100 

 per cent alcohol. 



5. 10 per cent Venetian turpentine 2 in an exsiccator until the turpentine 

 becomes thick enough for mounting. 



6. Mount in the Venetian turpentine. 



1 Pfeiffer, Ferdinand, and Wellheim, R. v., "Zur Preparation der Susswasseralgen," 

 Jahrbiicher filr wissenschaftliche Botanik, 26:674-732, 1894. 



2 The Venetian turpentine which we have used is marked "Venice Turpentine 

 (true)." It can be obtained from Morrison, Plummer & Co., Chicago, Illinois. 



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