ZOOLOaY AND BOTANY, MICROSCOPY, ETC. 231 



2. Vasculose. This is the substance which enters most largely 

 into the composition of vessels and tracheids. It usually accompanies 

 cellulose-substances, but differs from them completely in composition 

 and properties, containing more carbon and less hydrogen. It is the 

 substance which, in certain cases, unites the cells and the fibres. It 

 sometimes occurs on the exterior of tissues in the form of a continuous 

 resisting and horny membrane. It forms in fact the solid part of 

 woody tissues; it is abundant in hard woods and in the scleren- 

 chymatous concretions in pears ; the shells of nuts and the stones of 

 stone-fruit often consist of this substance to more than half of their 

 weight. Vasculose is insoluble in bihydrated sulphuric acid and in 

 the copper reagent ; it does not dissolve sensibly at the ordinary 

 pressure in alkaline solvents, but only with the assistance of pressure. 

 This important property is utilized in the manufacture of paper from 

 straw and wood. It dissolves rapidly in oxidizing substances, as 

 chlorine water, hypochlorites, nitric acid, chromic acid, perman- 

 ganates, &c. Before dissolving it, oxidizers change it into a resinous 

 acid soluble in alkalies. Cellulose-substances can be removed from 

 vasculose by the solvent action on them of bihydrated sulphuric acid 

 or Schweitzer's reagent. If, on the other hand, these substances have 

 to be freed from vasculose, the tissue is subjected for several hours to 

 the action of nitric acid diluted with its volume of water in the cold, 

 which does not act sensibly on cellulose-substances, while it transforms 

 the vasculose into a yellow resinous acid which can then be dissolved 

 out by means of an alkali. 



3. Cutose. This substance constitutes the fine transparent mem- 

 brane which forms the surface of the aerial parts of plants ; the 

 " suberine " of Chevreul is a compound of cutose and vasculose. It 

 possesses several characters in common with vasculose, resisting the 

 action of bihydrated sulphuric acid ; but it is soluble at the ordinary 

 pressure in dilute or carbonated solutions of potassa and soda. It 

 contains more carbon and hydrogen than vasculose. Subjected to the 

 action of nitric acid, it gives rise to suberic acid. To separate cutose 

 from the cellulose-substances and from vasculose, the copper reagent 

 is first used to dissolve the former, and the tissue is then agitated 

 with potassa at the ordinary or at a higher pressure, the former 

 dissolving the cutose and the latter the vasculose. 



4. Pedose. This substance is insoluble in water, but is dissolved 

 by the action of dilute acids and converted into pectine. It occurs 

 ordinarily in the utricular tissues of roots and fruits, and is recognized 

 by subjecting the tissue with heat to the action of dilute hydrochloric 

 acid ; it then forms pectine, which is dissolved in the water and can 

 be precipitated by alcohol. 



5. Calcium pedate. This salt is often the basis of a tissue which 

 occurs in the form of a continuous membrane, serving, as in the pith 

 of certain trees, to bind the cells together. If this salt is decomposed 

 by an acid, the tissue is immediately disintegrated into its constituent 

 cells. Its determination is effected by heating the tissue in the cold 

 with dilute hydrochloric acid, which decomposes the calcium pectate, 

 leaving the pectic acid in an insoluble state ; this is then heated with 



