Rudolf Beer. 159 
THE PRESENT POSITION OF CELL-WALL 
RESEARCH. 
N the following note a brief outline is given of some of the 
principal directions along which research into the constitution 
of the cell-wall has moved during the last few years. 
Until quite recently the chemistry of the cell-wall was believed 
to be comparatively simple. ’ It was thought that the cellulose wall, 
which is first laid down, could either remain unchanged or it might 
subsequently become altered by lignification, cuticularisation or by 
mucilaginous changes. We now recognise that this account is 
wholly inadequate. It has been shown by various writers, notably 
by E. Schulze, that the cellulose of the older botanists is not a 
single body but a group of chemically allied substances. Schulze 
limits the term cellulose to that particular form which yields grape- 
sugar or dextrose on hydrolysis; a number of other similar bodies 
which do not split off dextrose but some other simple sugar 
(mannose, galactose, etc.) when they are hydrolysed are classed 
together as hemi-celluloses. Up to the present these hemi-celluloses 
have been almost entirely studied in connection with the seeds of 
various plants, especially (but not exclusively), in the thickened 
walls of the endosperm or cotyledon. Later research will no doubt 
show them to have a much wider distribution. The li reserve- 
cellulose ” found by Reiss in the endosperm of Phcenix dactylifera , 
Phytelephas, etc., is a member of the hemi-cellusoses. The amyloid 
studied by Nadelmann, Reiss and Winterstein in various seeds is 
probably an allied body but its true chemical position is still 
undecided. 
The pectic substances, first made known to us by the work of 
Payen, Braconnot, Mulder and Fremy, have been found by Mangin 
to have a very wide distribution in the cell walls of plants. Mangin 
classifies these substances into (1) Neutral pectic bodies, e.g. pectose 
and pectine ; (2) Acid pectic bodies, e.g - . pectic acid. In the inner 
layers of the cell-wall of a great many tissues pectose is found to be 
intimately associated with celluloses. The middle lamella is usually 
composed of calcium pectate. Pectose is readily converted into 
pectine and it has been suggested that the calcium pectate of the 
middle lamella arises from the transformation of pectine under the 
influence of the widely distributed enzyme pectase. 
In the opinion of many chemists pectic bodies are carbohydrates, 
