METABOLISM AND THE DISTRIBUTION OF MATERIAL 249 



1. Formation of cellulose hydrogel in the youngest plant tissues 

 as a chemically indifferent surface or framework. This primary 

 stage will be explained more fully. 



2. The colloidal constituents of cambial juice become layered upon 

 the cellulose surface by adsorption and gel-formation, and thus in- 

 crease the thickness of the surfaces. 



3. Chemical reactions occur between the adsorbed hydrogels which 

 lead to lignin formation. 



The following facts indicate the truth of these assumptions: 



(a) Colloidal constituents can be extracted by adsorption from the 

 cambial juice. 



(6) The colloids adsorbable from the cambial juice and the run- 

 ning sap are indicative of their lignin content, which means their 

 wood-forming properties. 



(c) The quantity of adsorbable colloidal constituents in the cambial 

 juice varies with the season of the year (shown in the annular 

 rings as early summer and late summer wood). 



Certain trees give such large quantities of spring sap on tapping, 

 that it is easy at times to collect a liter or more in a day. In North 

 America the sugar maple has this property. In Norway, Sweden 

 and Russia people drink the sap of the birch either fresh or fermented. 

 The trees are bored about 10 cm. deep, 30 to 40 cm. above the ground 

 and a glas^ tube is inserted and sealed in with tree-wax. The sap 

 drops through the bent tube into a bottle. 



To obtain the cambial sap, trunks of birch, pine and gray ash are 

 sawed into pieces, 15 to 20 cm. long. The bark from 7 to 15 kilos 

 of this is taken and then split vertically. The smooth inner layer 

 of the bark and the outer cambial mass of the smooth surface of 

 wood are well shaved off with glass. The shavings are placed in 

 from 1 to 2 liters of water and allowed to remain several hours, a few 

 drops of thymol solution being added. The water is poured off, the 

 residue squeezed in a fruit press and the combined turbid fluids are 

 filtered. 



The adsorption experiments were performed partly by shaking 

 with finely divided cellulose (filter paper) and partly by siphoning 

 through "washed clay." (See p. 110.) In both cases the quantity 

 of material adsorbed was estimated by determining the weight of 

 the dried residue of (a) a measured quantity of fluid before adsorp- 

 tion, (6) the same volume after adsorption. 



H. WISLICENUS was able to prove in the case of the rising sap 

 obtained by tapping the hornbeam and in the cambial juice of the 

 birch, that the abstraction of colloidal substances followed an adsorp- 

 tion curve, because the more dilute the solutions the more colloida 1 



