New York AGRICULTURAL EXPERIMENT STATION. 177 
They term groups (a) and (b) tne celluloses proper. Group 
(c) is held to be quite different from these, but for convenience 
of treatment they allow it to remain in the larger group, ac- 
cepting Schultze’s name as satisfactory, viz., pseudo-cellulose 
or hemicellulose. As defined more exactly the hemicelluloses 
are “substances closely resembling in appearance the true cel- 
luloses but easily resolved into simpler carbohydrates by the 
hydrolytic action of enzym or of the dilute acids or alkalies.” 
We are, however, chiefly concerned with the compound cellu- 
loses which Cross and Bevan term “ pecto-celluloses,” since 
these constitute the middle lamella and other wall. elements 
acted upon by the carrot-rot enzym. The present understand- 
ing of these dates from the work of Fremy (1840, 1848), who 
found in plant cell walls, along with cellulose, another sub- 
stance which he called pectose. He also isolated from carrot 
roots and other plant tissues an enzym “ pectase ” capable of 
gelatinizing this pectose and related compounds, which will 
be discussed in more detail iater. Subsequently chemists have 
confirmed Fremy’s observations and conclusions and class the 
pectose series of compounds with the celluloses as indicated in 
the discussion above from Cross and Bevan. Mangin has re- 
cently (1888-1893) made most extensive studies upon these 
matters and shows that here again we have not a simple com- 
pound but a complex of closely related compounds. These he 
divides into two natural series, the one neutral, the other 
acid. Pectose is one of the less soluble neutral series, and 
pectine is a more soluble form. Both of these are of aide 
distribution, especially in the walls of voung tissues. Of the 
‘acid series pectic acid is of common occurrence and peculiar 
interest to us and especially its insoluble salt calcium pectate. 
Fremy supposed that when his enzym, pectase, clotted the pec- 
tose solutions it did so by converting the pectose into pectic 
acid. Bertrand and Mallevre (1894, 1895) have recently shown 
that this clot is, however, calcium pectate. Payen’™ believed 
that the middle lamella consist largely if not wholly of this 
salt, and the recent studies of Mangin and Bertrand-Mallevre 
2 Cf. Green 1901: 248, 
