CELL WALL. 
39 
of stems and roots it is combined with suberin or 
suberose. This class of celluloses is distinguished from 
cotton cellulose and lignocellulose by being insoluble 
in sulphuric acid. 
(3) Reserve cellulose walls are those found in various 
seeds, as in coffee, date, nux vomica, etc. They 
behave toward reagents much like the true celluloses. 
(4) Mucilage cellulose walls consist of cellulose and 
mucilage and are found in all parts of the plant, and 
in the case of seeds are associated with the protective 
celluloses. They dissolve or swell in water, are colored 
blue or yellowish with iodine, and are stained with 
alcoholic or glycerin solutions of methylene blue. 
(5) Mineral cellulose walls are composed of cellulose 
and various inorganic substances, as silica, calcium 
oxalate or calcium carbonate. These are more com- 
monly found in the cell wall of the lower plants, as 
algse, fungi and Equisetacere. Calcium carbonate also 
occurs in the cystoliths of the various genera of the 
UrticaceEe. 
From what has just been said of the chemical compo- 
sition and structure of the cell wall, it is seen that it 
consists of lamellse or layers of different substances, 
and in no case does it consist of but a single substance; 
but for convenience we speak of a wall as consisting of 
cellulose, lignin, or suberin, meaning thereby that the 
wall gives characteristic reactions for these substances. 
In some cells, as in lignified cells, the lamellse are 
quite apparent, whereas, in other cases, the use of 
reagents, as chromic acid, or chlor-zinc-iodide, is neces- 
sary to bring out this structure. The layering which 
is observed in transverse sections of the cell wall is 
spoken of as stratification of the wall, whereas, the layer- 
ing observed in longitudinal or tangential sections is 
referred to as striation of the wall. 
