4 “BOTANICAL GAZETTE [ JULY 
that a cell wall may be visible here before the cell plate by 
peripheral growth has reached the mother cell wall. 
Mangin (3, 4)5, 6, 7, 8), in a series of contributions which 
appeared from 1888 to 1893, investigated particularly the chemi- 
cal nature of the substance in question. As this side of the sub- 
ject and Mangin’s very interesting conclusions regarding it have 
been little discussed, a somewhat full résumé of his results may 
here be given. 
Dippel, quoted by Mangin (3), had already announced that 
the new partition deposited by the protoplasm has none of the 
properties of cellulose. Frémy found in the tissues of fruits and 
roots a substarice called by him pectose, which he was unable 
to separate from cellulose, and from which ate produced the 
pectic compounds found in the walls of fruits.: Maudet found 
in the pith of certain trees pectose and calcium pectate, form- 
ing a cement which holds the cells together. .Mangin (3) found 
plant cell walls to be generally formed by the association of two 
substances, cellulose and one which he provisionally called 
pectose. Ina large variety of adult tissues he found _pectose, 
in a pure state, forming the middle lamella or intercellular sub- 
stance, and associated with cellulose in the other layers of the 
cell wall. Dippel’s conclusion, that the middle lamella is free 
from cellulose, was thus confirmed. Some tissues ‘were found to 
be composed wholly of pectose. It plays the principal réle in 
what had been called cellulose fermentation, and Mangin con- _ 
sidered chemical modifications of cell walls, as lignification and 
cutinization, to be due to transformations of pectose, of which 
cellulose is incapable. At this time (1888) he repeatedly speaks 
of the pectose layer as the first membrane formed in cell 
division, the “fundamental! layer of the cellular membrane.” 
This seems to indicate an acceptance of the view then! held by 
Strasburger as to the identity ofthe mss soni with the 
cell plate. 
But’ in’ 1890, Mangin (5) suggested the Psuiihraseacsss sot 
restoring to this layer the name ‘‘intercellular’substance,” as 
expressing better than that of ‘‘middle lamella” its ‘origin and 
