256 A TEXT-BOOK OF BOTANY. 



use of potassium hydroxide ; to this is then added a mucilaginous 

 layer, as in the secretion cells of Valeriana officinalis and Magnolia 

 grandiflora. 4. The outer layer may be suberized, but the cellulose 

 layer beneath this is not colored blue until the walls have been 

 first treated with Schultze's solution; this then is followed by a 

 mucilaginous layer, e.g., Piper nigrum, Piper Cubeba, and Sassa- 

 fras oMcinale. 5. The outer and inner layers may be suberized, 

 and between these are fine lamellae of cellulose, e.g., Croton 

 Eluteria. 6. The outer layer may be suberized, beneath which is 

 a layer of lignocellulose, followed by a mucilaginous layer, e.g., 

 Calycanthus floridus. 7. The outer layer may be colored yellow 

 with chlor-zinc iodide and dissolves in sulphuric acid, while the 

 inner layer is suberized, e.g., fruit of Conium maculatum. 



CELLULOSE in its various modifications constitutes the greater 

 proportion of the cell-wall. The cellulose making up the cotton 

 fiber may be said to be the typical cellulose, and is known as 

 " cotton cellulose." It is soluble in copper ammonium sulphate 

 solution ; is colored blue with chlor-zinc-iodide solution or iodine 

 and sulphuric acid, and is stained by acid phenolic dyes, as alizarin, 

 if previously treated with basic mordants, as basic salts of 

 aluminum, etc. 



The following solutions are used in the testing of mixed 

 fabrics containing cotton : i. A solution of i part of zinc chloride 

 in 2 parts of hydrochloric acid will dissolve cellulose in about 

 one-half minute. 2. Upon heating a piece of fabric in a saturated 

 solution of aluminum chloride, the cotton becomes friable, the 

 wool remaining unaffected. 



According to their origin in the plant, or their behavior toward 

 reagents, the cellulose walls may be divided into the following 

 groups: (i) Lignocellulose walls; (2) protective cellulose walls; 

 (3) reserve cellulose walls; (4) mucilage cellulose walls, and (5) 

 mineral cellulose walls. 



Lignocellulose walls are composed of true cellulose and a 

 non-cellulose (the so-called lignin or lignone), these constituting 

 the woody (so-called lignified) portion of plants and, in some 

 instances, also the bast portion of the bark. The lignocelluloses 

 are colored yellow with chlor-zinc iodide, or iodine and sulphuric 

 acid, On account of their containing in some instances furfurol, 



