312 REAGENTS AND PROCESSES 



■diluted with water as is found necessary. A rather pale solution 

 of iodine is sufficient to color starch blue. To stain modified 

 cell-walls the solution needs to be stronger. 



Iodine Green. — See page 266 for the use of iodine green in 

 double staining. A 2 per cent, solution of glacial acetic acid 

 with iodine green dissolved in it serves well in the instant fixing 

 and staining of the nuclei of fresh material. 



Iron Acetate. — Used in the detection of tannins, which see 

 in the next chapter. 



Lactic Acid. — Dried algae and fungi may be prepared for 

 study with the microscope by soaking them first in water and 

 then in concentrated lactic acid, in which they are heated until 

 small bubbles are formed; they may then be studied in the 

 lactic acid. A 10 per cent, solution of lactic acid is recommended 

 for fixing bacteria. This fixative is said not to interfere in any 

 way with the subsequent processes of staining with alcoholic 

 solutions of aniline dyes. 



Lead Acetate. — A 10 per cent, solution of neutral lead acetate 

 is used to harden the mucilaginous layers of seed coats. For 

 subsequent treatment see under Boracic Acid. 



Lithium Carbonate. — Useful in removing from material 

 picric acid, which has been used as a fixative. A few drops 

 of a cold, saturated, aqueous solution of lithium carbonate are 

 added to the alcohol, used to wash out the fixative. 



Maceration. — In studying the forms of cells it is sometimes 

 desirable and even necessary to isolate them by the process of 

 maceration. Where cells with lignified walls are to be isolated 

 Schultze's maceration process is best employed. Put a small 

 amount of concentrated nitric acid into a test-tube and add 

 a small crystal of potassium chlorate. Heat this to boiling 

 and drop into it sections containing the tissues under investi- 

 gation. The sections will soon turn quite white. When this 

 occurs, and before the sections have time to dissolve altogether, 

 pour the contents of the test-tube into a large dish of water. 

 Select a section and tease it out in a drop of water on a glass 

 slide with dissecting needles, and examine the preparation 



