4 8o SCIENCE PROGRESS. 



these cellulose-reserves. The cell wall, thus, as well as 

 the cavities of the cells must be examined carefully, in 

 estimating the carbohydrate reserve materials. 



During the last few years a great deal of research has 

 been directed to ascertaining exactly what is the composi- 

 tion of this cell-membrane, and it has resulted in establish- 

 ing clearly that instead of this being fairly uniform in its 

 composition, and consisting of cellulose, and the products 

 of its decomposition, it is an extremely complex substance, 

 varying in different cases and usually containing, besides 

 cellulose, a certain, often considerable, amount of substances 

 till recently somewhat crudely described as pectic bodies. 



The investigation of these latter is not a new departure. 

 Long ago Fremy studied them carefully as far as the 

 chemistry of his time would permit, and he has described 

 certain of them which he found to exist in the pulp of 

 certain fleshy roots, particularly those of the carrot and the 

 beet. Fremy (41) pointed out that some substance which 

 he named pectose existed in the cell wall side by side with 

 cellulose, and spoke of its conversion by the action of a 

 special enzyme into two gelatinous bodies, to which he gave 

 the names of pectosic and pectic acids. These were the 

 result of the hydrolysis of pectose and differed from each 

 other in the amount of water they severally contained. 



In more recent years these pectic bodies have been the 

 subject of several papers by Mangin (42), who has made 

 extended investigations into their occurrence in almost all 

 the larger groups of the vegetable kingdom. He finds 

 them in Algae, Fungi, Mosses, Vascular Cryptogams and 

 Phanerogams, in most organs and in most diverse plants. 



As the result of his work, we may say that at least 

 four definite bodies may be prepared, which have been 

 by the older writers included vaguely in the one term 

 pectic bodies. These may be divided into two groups 

 or series of bodies, for there seem to be probably in- 

 termediate ones between those clearly established ; the 

 two series differing from each other in that one con- 

 sists of neutral, the other of acid ones. The reason for 

 supposing that intermediate members of each series exist 



