Researches on Cellulose | Page 5

but the researches of Gilson ('La Cristallisation de la
Cellulose et la Composition Chimique de la Membrane Cellulaire
Végétale,' 'La Revue,' 'La Cellule,' i. ix.) are an important contribution
to the natural history of cellulose, especially in relation to the 'pectic'
constituents of the parenchymatous celluloses. Indirectly also the
researches of Tollens on the 'pectins' have contributed to the subject in
correcting some of the views which have had a text-book currency for a
long period. These are dealt with on p. 151. The results establish that
the pectins are rather the soluble hydrated form of cellulosic aggregates
in which acid groups may be represented; but such groups are not to be
regarded as essentially characteristic of this class of compounds.
~Furfural-yielding Substances~ (Furfuroids).--This group of plant
products has been, by later investigations, more definitely and
exclusively connected with the celluloses--i.e. with the more permanent
of plant tissues. From the characteristic property of yielding furfural,

which they have in common with the pentoses, they have been assumed
to be the anhydrides of these C{5} sugars or pentosanes; but the direct
evidence for this assumption has been shown to be wanting. In regard
to their origin the indirect evidences which have accumulated all point
to their formation in the plant from hexoses. Of special interest, in its
bearings on this point, is the direct transformation of levulose into
furfural derivatives, which takes place under the action of condensing
agents. The most characteristic is that produced by the action of
anhydrous hydrobromic acid in presence of ether [Fenton], yielding a
brommethyl furfural
C{6}H{12}O{6} - 4H{2}O + HBr = C{5}H{3}.O{2}.CH{2}Br
with a Br atom in the methyl group. These researches of Fenton's
appear to us to have the most obvious and direct bearings upon the
genetic relationships of the plant furfuroids and not only per se. To give
them their full significance we must recall the later researches of
Brown and Morris, which establish that cane sugar is a primary or
direct product of assimilation, and that starch, which had been
assumed to be a species of universal matière première, is probably
rather a general reserve for the elaborating work of the plant. If now
the aldose groups tend to pass over into the starch form, representing a
temporary overflow product of the assimilating energy, it would appear
that the ketose or levulose groups are preferentially used up in the
elaboration of the permanent tissue. We must also take into
consideration the researches of Lobry de Bruyn showing the labile
functions of the typical CO group in both aldoses and hexoses, whence
we may conclude that in the plant-cell the transition from dextrose to
levulose is a very simple and often occurring process.
We ourselves have contributed a link in this chain of evidence
connecting the furfuroids of the plant with levulose or other
keto-hexose. We have shown that the hydroxyfurfurals are constituents
of the lignocelluloses. The proportion present in the free state is small,
and it is not difficult to show that they are products of breakdown of the
lignone groups. If we assume that such groups are derived ultimately
from levulose, we have to account for the detachment of the methyl

group. This, however, is not difficult, and we need only call to mind
that the lignocelluloses are characterised by the presence of methoxy
groups and a residue which is directly and easily hydrolysed to acetic
acid. Moreover, the condensation need not be assumed to be a simple
dehydration with attendant rearrangement; it may very well be
accompanied or preceded by fixation of oxygen. Leaving out the
hypothetical discussion of minor variations, there is a marked
convergence of the evidence as to the main facts which establish the
general relationships of the furfuroid group. This group includes both
saturated and unsaturated or condensed compounds. The former are
constituents of celluloses, the latter of the lignone complex of the
lignocelluloses.
The actual production of furfural by boiling with condensing acids is a
quantitative measure of only a portion, i.e. certain members of the
group. The hydroxyfurfurals, not being volatile, are not measured in
this way. By secondary reactions they may yield some furfural, but as
they are highly reactive compounds, and most readily condensed, they
are for the most part converted into complex 'tarry' products. Hence we
have no means, as yet, of estimating those tissue constituents which
yield hydroxyfurfurals; also we have no measure of the furfurane-rings
existing performed in such a condensed complex as lignone. But,
chemists having added in the last few years a large number of facts and
well-defined probabilities, it is clear that the further investigation of
the furfuroid group will take its stand upon a much more adequate
basis than heretofore. On the view of 'furfural-yielding' being
co-extensive with 'pentose or pentosane,' not only were a number of