CHAPTER XLVII 



SOME SPECIAL METHODS MACERATION CLEARING 



BLEACHING CELL-WALL SUBSTANCES 



1264. Maceration Methods. For a full account see Kisser 

 {Handb. Biol. A rbe its method en (Abderhalden), Abt., xi, 1931, 

 Teil iv, p. 285). 



The living cells of some plants become separated from one 

 another when they are grown in air containing camphor vapour, 

 ether, coal gas and some other substances. Other vapours should 

 be tried. Also plant parts left in solutions of certain nutrient 

 salts become separated into individual cells. Thus root-tips of 

 Lupimts alhus dissociate after twenty to twenty-four hours in 

 M/lOO potassium or magnesium chlorides. 



Most methods depend on the ready solution, by various reagents, 

 of the middle lamella, which is usually of a pectic nature. Thus 

 many objects respond to treatment with acid alcohol, followed 

 by ammonia. The principal reagents used are boiling water, 

 freezing, retting, organic acids (malic, citric, oxalic, acetic, tartaric), 

 chromic acid, Schultze's reagent, mineral acids, aqua regia (HNO3 

 — HCl), strong alkalies, hydrogen peroxide, eau de Javelle. 



The epidermis, for hairs and stomata, is stripped mechanically 

 with the aid of a sharp scalpel. Use the leaf or stem in a turgid 

 or but slightly wilted condition. Cut a slit in the epidermis and 

 slip the tip of the scalpel in under the epidermis. In difficult 

 cases scald or boil the leaves in water. Or boil in a 5 per cent, 

 solution of caustic potash until the tissues are translucent and 

 the epidermis separates readily ; wash in water. 



Heilborn {Svensk. Bot. Tidskr., xxvii, 1933, p. 161) counts 

 cell numbers or ])ollen grain numbers in plants by macerating 

 (or powdering) portions and mixing the material with a test 

 substance in which the number of particles per milligram is 

 known. 



Macerating Xylem. Here the middle lamella is of lignin. In 

 the cases of herbaceous monocotyledons and ferns first remove the 

 vascular bundles from the ground tissue by hand and cut them 

 into short lengths. Cut perennial woody specimens into longi- 

 tudinal shavings. It is best to use hot strong (30 per cent, or 

 more) chromic acid ; or. chromic acid in conjunction with nitric 

 acid, both at 5 to 10 per cent, strength, either in the cold or heated 

 on a Avater bath. A more violent method is to boil the material 



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