106 FKUITS AND FRUIT PEODUCTS. 



by using a centrifuge. By decanting the supernatant liquid and plac- 

 ing the final product in a large watch glass a macroscopic examination 

 can be made, which will usually be found suggestive as to the proba- 

 ble components. Portions can then be mounted for microscopic 

 examination. 



TECHNIQUE OF EXAMINATION. 



The examination for starch in cells is made by iodine in potassium 

 iodide solution. 



To examine the pulp cells a sample was fixed to the slide by evapo- 

 rating to diyness at about 50, or by smearing the slide with Mayer's 

 albumen fixative before putting the sample upon it and then rinsing 

 with 90 per cent alcohol before beginning the staining process. The 

 former method, however, was found more satisfactory. For a tempo- 

 rary mount no clearing agent is used. For Adams's test the best 

 results were obtained by using a- solution of Griibler's dahlia, made up 

 according to the usual formula (dry stain, 1 gram; anilin water, 80 cc; 

 05 per cent alcohol, 20 cc). A drop of stain was added and allowed to 

 act one minute, rinsed in water carefully thirty seconds to remove 

 excess stain, and then treated with iodine solution thirt} T seconds before 

 covering. For permanent specimens Gram's gentian violet or anilin 

 safranine (these stains are made up of dry stain, 1 gram; alcohol, 20 cc; 

 anilin oil, 3 cc; water, 80 cc) gives good results when sections are 

 mounted in balsam. If the material is stained two to three hours in 

 the safranine and then after rinsing with water stained for one minute 

 in gentian violet, the stone cells are differentiated from the pulp cells, 

 since, being composed of lignified tissue, they take the safranine well, 

 but very slowly the gentian violet which, on the other hand, stains 

 the cellulose pulp cells verv readily. 



The scheme of identification outlined is quite largely based upon an 

 examination of the components of the fibro-vascular bundles, which in 

 many cases have characteristic elements. The sample for such exam- 

 ination is mounted in a drop of chloral hydrate (crystals 8 parts, 

 water 5 parts) and heated for a few seconds to boiling, covered, and by 

 gently tapping the cover glass the bundle is broken up into its ele- 

 ments. Marpmann a recommends the use of alcoholic phenol as a 

 clearing agent, but we have used chloral hydrate with better results, 

 and it has the advantage of assisting in the maceration process. 



A second method consists of staining with acetic acid-methyl green, 

 and after withdrawing the excess of stain with a strip of filter paper 

 and mounting in water, separating the component elements by tapping 

 the cover glass as before. By this means the elements are easily dis- 

 tinguished, though they are not cleared, as in the chloral-hydrate 

 method. 



"Ztschr. ange. Mikros., II. Bd., 4 Heft, p. 97. 



