90 MICROSCOPICAL TECHNIQUE. 



solved, and filtered, evaporate over a water-bath to the consistency 

 of thick syrup. Dallinger, in his new book, makes the useful sug- 

 gestion that cement-rings should be so finished that, when the 

 objects are examined by means of immersion objectives, the rings 

 will be unaffected by the cedar-oil used as immersion fluid. 

 Hollis's liquid glue, or a varnish made by dissolving shellac or 

 good sealing-wax in strong alcohol, will effect the desired purpose 

 when thinly brushed over the edges of the mounts, however closed 

 and finished. The Scientific Americayi gives a recipe for a trans- 

 parent cement composed of dammar 5 drs., mastic 3 drs., hard- 

 ened Canada balsam 3 drs., chloroform and rectified turpentine 

 each I fluid oz. Dissolve and filter. 



Biological Water Analysis.*— An instructive note by Geo. W 

 Rafter deals with the microscopical as distinct from the bacterial 

 analysis of water. The former deals with all forms of life that are 

 easily studied in all their phases by use of the microscope, includ- 

 ing algae, larger fungi, sponges, infusoria, rotifers, etc. The 

 various forms of apparatus used are figured and described and the 

 technique clearly explained. Special attention is devoted to 

 refinements in enumeration and measurement, and the work is 

 placed on a thoroughly scientific basis. 



Identification of Pectic Substances.f— The method recom- 

 mended by L. Mangin for determining the presence of these sub- 

 stances in plant-tissues is to wash sections with acetic acid (t"5 

 per cent.) ; then neutralise and treat with a mixture of naphthaline 

 blue R and acid green. The pectic compounds are stained violet 

 by the former, whilst lignin and suberin fix the green stain. By 

 acting on small pieces of tissue with dilute hydrochloric acid, or a 

 mixture of acid, i part, and alcohol, 3 parts, pectic acid, if present, 

 will be separated from the base (usually lime, with which it is 

 combined). It is quite insoluble in water, but may be dissolved 

 by the action of a weak alkali, and then precipitated in gelatinous 

 flakes by a weak acid. Pectose is found associated with the 

 calcium pectate, but is not readily isolated, remaining behind after 

 the action of the alkali. 



* Amer. Mon. Micro. Journ., March, 1892. 

 i /ourn. de Bot.^ Vol. VI., p. 363, in Phai m. Journ. 



