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 _matiere premiere_, 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 th