ZOOLOGY AND BOTANY, MICROSCOPY, ETC, 233 



eliminated, is almost entirely composed of cellulose. The testa is 

 formed of a mixture of cutose, cellulose, and paracellulose, producing 

 a series of resisting and horny envelopes. 



The tissues of fungi, including several species of PenicilUum, 

 contain large quantities of metacellulose, the " fungine " of 

 Braconnot. 



Vasculose is a constituent of almost all vegetable tissues, associated 

 with cellulose ; it forms the greater part of vessels and tracheids. In 

 the parenchyma of the pith and in woody tissues it unites together the 

 cells. At the surface of roots and fruits it often forms a continuous 

 transparent horny membrane. The proportion of vasculose corre- 

 sponds, in general terms, to the resistance or hardness of the tissue. 

 The wood of the poplar contains about 18 percent, of vasculose ; that 

 of the box 34 per cent. ; ebony and lignum-vitse 35 per cent. ; iron- 

 wood 40 per cent. The stony concretions of pears, the shell of the 

 hazel, walnut, and cocoa-nut, and the stone of the apricot and peach, 

 may contain as much as 60 per cent, of vasculose. 



Vasculose can be obtained in special purity from the pith of the 

 elder. After treating with dilute alkali, it is boiled with dilute 

 hydrochloric acid, in order to transform the paracellulose into 

 cellulose ; the ammoniacal copper (Schweitzer's) reagent is then used ; 

 and the treatment repeated eight or ten times until no further reaction 

 ensues. The pure vasculose thus obtained preserves a light yellow 

 tint, maintaining the structure of the original tissue. 



"Vasculose is insoluble in all neutral solvents; it is not altered 

 when boiled with dilute sulphuric, hydrochloric, or phosphoric acid ; 

 it resists the action of trihydi'ated sulphuric acid ; it is not changed 

 by boiling alkaline solutions ; concentrated sulphuric acid only 

 colours by dehydrating it. It is, however, rapidly changed by 

 oxidizing agents, such as nitric or chromic acid, potassium perman- 

 ganate, chlorine, bromine, hypochlorites, &c., producing resinous acids. 

 Those which are first formed are not sensibly soluble in alcohol ; those 

 last formed dissolve in alcohol, and even in ether. They contain. 

 less hydrogen and more oxygen than vasculose. The oxygen of the 

 air at length acts on vasculose, transforming it into resinous acids 

 soluble in alkalies ; this being the cause of the change which certain 

 woods undergo in contact with the air. It dissolves rapidly when 

 heated, under pressure, at a temperature of about 130° C, with 

 caustic alkalies. The products are again a series of acids at first in- 

 soluble in alcohol ; those formed later being soluble in alcohol, and 

 finally in ether. Baryta and lime produce the same result. It is this 

 reaction of vasculose which is utilized in the manufacture of paper 

 from wood and straw. Heated with fused potassium hydrate, vasculose 

 is at once transformed into ulmic acid ; cellulose giving rise, under 

 similar circumstances, to acetic and oxalic acids. 



One of the principal results of the distillation of vasculose is 

 methyl-alcohol ; in the distillation of wood, this substance is in great 

 part the source of the acetic acid. It is well known that those woods 

 which produce, on distillation, the largest amount of pyroligneous 

 acid are the heavy woods, which are therefore most rich in vasculose. 



