Using water‐soluble araboxylan of rye as substrate, it is shown that enzymic degradation involves four enzymes or enzyme systems: (a) arabinosidase, liberating free arabinose from araboxylan and from oligosaccharides; (b) endoxylanase, degrading xylan chains, whether or not these carry arabinose side chains; (c) exoxylanase, producing xylobiose from araboxylan and from oligosaccharides after some degree of arabinose removal has been achieved; and (d) xylobiase, liberating free xylose from xylobiose and, perhaps, also from xylotriose. The first detectable low‐molecular product of the joint action of these enzymes is arabinose; xylobiose and xylose appear in detectable quantities somewhat later, and higher oligosaccharides later still. Oligosaccharides with back‐bone chains of up to six xylose residues have been observed, these carrying varying proportions of arabinose residues in side chains. Different raw cereals carry all four enzyme systems, but in different proportions; the malting enhancement of pentosanase activity in barley is small compared with the enhancement of β‐glucanase activity.

It is confirmed that the dissolution of hemicelluloses (gums) which occurs when barley grist is mixed with water depends primarily on purely mechanical factors which influence penetration of the grist particles by the solvent; the dissolution can, however, be accelerated in its early stages by enzyme action. Apart from an appar ently minor degree of solubilization of initially insoluble hemicelluloses, the enzymic action is indirect, being proteolytic rather than cytolytic. A major final product of degradation of the dissolved hemicelluloses is glucose, though arabinose, xylose and pentose oligosaccharides are also formed; a substantial amount of maltose is also produced, probably from water-soluble a-glucan. The changes observed in this autolytic procedure are considered to be of significance during steeping and in those stages of growth in malting which precede the rapid development of amylolytic, cytolytic and proteolytic enzymes.

During the autolysis of barley the pattern of behaviour of water‐soluble pentosans is obscured by the massive changes in β‐glucan, though the amounts of soluble pentosans increase during the 4‐hr, autolysis period applied. Mechanical factors appear to play an important part in pentosan solubilization, both in regard to simple penetration of the tissue by the solvent and also to the influence on this penetration of the enzymolysis of non‐pentosan materials, particularly, perhaps, β‐glucan and protein; this conclusion seems to have special significance during the early days of malting, and emphasizes the importance which should be attached to the physical condition of the grain.

Schwarz avtd MacDougall. 3065 592. Benxyloxyrnalondialehyde. An Intermediate in the Oxidation of 2 -0 -Ben2 y 1 -D -ara b inose with Sodium Period ate. By J. C . P. SCHWARZ and (in part) MYRA MACDOUGALL. Benzyloxymalondialdehyde has been isolated as an intermediate in the oxidation of 2-0-benzyl-D-arabinose with periodate, and its reactions have been investigated.