close a genetic connection.

The _lignocelluloses_ have been further investigated. Certain new types
have been added, notably a soluble or 'pectic' form isolated from the
juice of the white currant (p. 152), and the pith-like wood of the
AEschynomene (p. 135).

Further researches on the typical fibrous lignocellulose have given us a
basis for correcting some of the conclusions recorded in our original
work, and a study of the esters has thrown some light on the
constitution of the complex (p. 130).

Of importance also is the identification of the hydroxyfurfurals as
constituents of the lignocelluloses generally, and the proof that the
characteristic colour-reactions with phenols (phloroglucinol) may be
ascribed to the presence of these compounds (p. 116).

The _pectocelluloses_ have not been the subject of systematic chemical
investigation, but the researches of Gilson ('La Cristallisation de la
Cellulose et la Composition Chimique de la Membrane Cellulaire
Vegetale,' '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