INSOLUBLE CARBOHYDRATES OR MARC. 87 



In this connection the following quotation from Cross and Bevan rt 

 is of interest: 



It appears, therefore, generally, that the pectic group are compounds of carbo- 

 hydrates of varied constitution with acid groups of undetermined constitution, asso- 

 ciated together to form molecular complexes, more or less homogeneous, but entirely 

 resolved by the continued action of simple hydrolytic agencies; and the pectocellu- 

 loses are substances of similar character in which the carbohydrates are in part 

 replaced by nonhydrolyzable celluloses. The general characteristics of the pecto- 

 celluloses are therefore these: they are resolved by boiling with dilute alkaline solu- 

 tions into cellulose (insoluble) and soluble derivatives of the noncellulose (pectin, 

 pectic acid, metapectic acid); they are gelatinized under the alkaline treatment; 

 they are " saturated compounds," not reacting with the halogens, nor containing 

 smy groups immediately allied to the aromatic series. 



Later in the same volume, page 221, Cross and Bevan refer to the 

 parenchymatous tissue of fruits, fleshy roots, etc., as being typical 

 pectocelluloses. 



Tins suggests the possibility that all insoluble pectin bodies occur- 

 ring in the vegetable world are really in combination with cellulose 

 and belong to the group of pecto.celluloses. This idea is in part borne 

 out by the results previously published by several writers and con- 

 firmed by the results given on page 88, in which it is seen that insolu- 

 ble pectin bodies are changed to soluble form by boiling with water. 

 If such insoluble pectin bodies, usually called pectoses, are really 

 poctocelluloses, this action by which they are converted into soluble 

 form is really a splitting off of the pectin group from the cellulose 

 complex. 



In this connection should be noted the recent work by Mangin, 6 in 

 which attention is called to deposits which that writer considered to 

 be calcium pectatc between the cell walls of plant tissues. His con- 

 clusions, however, have recently been disputed by Devaux, c who 

 asserts that this insoluble deposit was not really calcium pectate but 

 true pectose. If it is found that the substance now known as pectose 

 is really a pectocellulose, it is suggested by the writers that the latter 

 term be employed to designate it and that the use of the term pectose, 

 which is a misnomer and altogether misleading, be discontinued. 



ANALYSES OF APPLE MARC. 

 PREPARATION OF SAMPLE. 



Fully ripe Rhode Island Greening apples were taken from cold 

 storage, wiped off, quartered, cores and bruised places removed, and 

 passed through a meat grinder. The pulp was then exhausted with 

 water by pressing out by hand in cloth bags with successive portions 



Cellulose, 2d eel., 1903, p. 217. 



''Loc. cit. (see p. 78). ' 



c Memoires de la societe den sri<Mi<v,s physiques et naturelles de Bordeaux, 1 '.!(): 

 [<>], 3: 90. 



