270 Cellulose 



treated with a little antichlor (sulphite of soda), and again washed. 

 It is then pressed up in suitable moulds, which may be easily made 

 by attaching perforated zinc to square frames of wood. Further 

 than this, if it is required to make an actual paper-making experi- 

 ment with pulp, this must be prepared by beating in a model 

 beater, and then converted into sheets by the hand process. The 

 details of such manipulation are, of course, highly technical, and for 

 organising such a plant and process, the assistance of an expert 

 would be required. Having determined the yield of cellulose by 

 the laboratory method, and ascertained its characteristics, the yield 

 by the alkali boiling and bleaching process, and the proportions 

 of caustic soda and of bleaching powder required for the isola- 

 tion of the pure cellulose, complete data are at hand for valuing 

 the raw material by comparison with staple materials of the same 

 class. 



The application of these methods to the investigation of green 

 plants in physiological investigations, or to fodder plants, green or 

 otherwise, is a province in which it is difficult to lay down definite 

 schemes. The choice of method must depend largely upon the 

 subject to be investigated, and for the present that is to say, until 

 our knowledge is more complete the selection must remain more 

 or less arbitrary. The following general considerations will serve 

 as guides in selecting methods suitable for particular inquiries. 

 Thus in green plants it is important to distinguish between what 

 we may call ' permanent ' or fundamental tissue, and cellulose or 

 lignocellulose. The fundamental tissue might be defined as the 

 assemblage of cells which constitute the plant, or part of the plant, 

 less the cell contents, including all excreted products. Therefore, 

 to isolate such a complex we must proceed by way of selecting 

 reagents calculated to remove particular constituents, or groups ot 

 constituents, with the least action upon the cell wall, or cell substance 

 proper, of whatever kind. In investigation of the permanent tissue 

 of the Gramineae which the authors are prosecuting, the following 

 process is used for its isolation : 



(1) The material is exhausted with boiling alcohol. 



(2) It is digested for 6 hours in cold dilute caustic soda (i p.ct. 

 NaOH). It is washed off from this solution, first cold and then 

 boiling hot. 



(3) It is digested for some hours in cold dilute hydrochloric acid 



