CELL-CONTENTS AND FORMS OF CELLS. 257 



coniferin, vanillin, cinnamic aldehyde, benzaldehyde or other alde- 

 hydic substances, they give definite color-reactions with certain 

 reagents. They are also stained by the aniline dyes, as fuchsin, 

 saf ranin, gentian violet, aniline blue, methylene blue, etc. 



Aniline hydrochloride with hydrochloric acid and aniline sul- 

 phate with sulphuric acid produce a golden-yellow color in cell- 

 walls containing lignocelluloses. 



A 2 per cent, phloroglucin solution, used in conjunction with 

 hydrochloric acid, gives a reddish-violet color with the lignocellu- 

 loses, although there are some celluloses of this class which do not 

 respond to this test, as flax (the bast fibers of Linum). In other 

 plants phloroglucin may occur as a constituent of the cells. 



Hartwich and Winckel (Arch. d. Phann., 1904, p. 462) have 

 shown that the red coloration formed upon the addition of vanillin 

 and hydrochloric acid to phloroglucin is also produced by a number 

 of other substances, viz., thymol, guaiacol, resorcin, cresorcin, 

 orcin, pyrogallol, pyrogallol dimethyl-ether, phloroglucin, oxy- 

 hydroquinone, eugenol, and safrol, but not with phenol, pyro- 

 catechin, hydroquinone, or pyrogallol trimethyl-ether. The re- 

 action cannot, therefore, be longer designated as a phloroglucin 

 reaction, but, in a limited sense, as a phenol reaction. The same 

 color reaction is produced by a number of other substances which 

 contain a phloroglucin molecule, e.g., phloridzin, maclurin, luteolin, 

 morin, catechin, filizin, gentisin, and all the phloroglycotannoides, 

 as in oak bark and cinchona bark. 



Protective cellulose walls are composed of mixtures of lig- 

 nocellulose and oils and waxes, and frequently contain in addi- 

 tion tannin, vanillin, and other compounds. In the cuticle or epi- 

 dermis of leaves and green stems the cellulose is associated with 

 a fatty compound known as cutin (or cutose), while in the cork 

 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. 



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 (Fig. 135). 



Mucilage cellulose walls consist of cellulose and mucilage, 

 and are found in all parts of the plant, and in the case of seeds 

 17 



