Compound Celluloses 203 



obtained by the process of chlorination, &c. By the latter 

 the authors obtain 60-65 P- ct - f cellulose from the coniferous 

 woods, whereas the ' sulphite process ' yields about 50 p.ct 

 This is another instance of the variable character of the ' cellu- 

 lose constants ' of fibrous products ; the cellulose being a 

 product of resolution or decomposition, and varying both in 

 character and proportion with the conditions of the treatment 

 by which isolated. 



With the exception of the woods of the Coniferae, none 

 of the woods have been submitted to exhaustive investigation 

 so far as regards the fundamental tissue or lignocellulose proper. 

 It appears, in fact, that such investigations have only been 

 tendered possible by the general advances of the science 

 during the last few years, more especially in the province of the 

 carbohydrates. This work upon the carbohydrates of lower 

 molecular weight, together with the preliminary work upon the 

 general features of lignifi cation recorded in this treatise, opens 

 out a very wide field for future work in the direction of reducing 

 the phenomena of elaboration and metabolism in the plant to 

 exact molecular expression. In regard to such investigations 

 we may point out here that of those types of lignification which 

 have been so far studied, four may be selected as showing well- 

 marked features of differentiation, viz. : 



' Annual ' products ' Perennial ' products 



Cereal straws j Jute bast Dicotyledonous woods ; Coniferous woods 

 I I 



each and all of which call for extended investigation, i.e. 

 individually as presenting a problem of chemical constitution, 

 anjd comparatively with the view to connect the variations in 

 composition with variations in the physiological factors of 

 their origin and growth. 



There are, of course, a number of woods characterised by 

 the secretion or excretion of particular products, such as more 



