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AFTER having shown that amino acids appear in the medium in inoculated, but otherwise sterile, quartz sand cultures of leguminous plants, we assumed that these amino acids are excreted from the nodules. The experimental evidence then available did not, however, exclude the possibility that the excretion might be a function of the roots.

THE excretion of nitrogen compounds from leguminous root nodules which has been demonstrated in this laboratory with a sterile culture system and, from the practical point of view, investigated with ordinary pot cultures, has not been shown in the pot cultures of all investigators1,2. With a sterile culture system Wilson has accomplished the excretion almost regularly3.

WITH reference to Prof. P. W. Wilson's communication upon this subject1 I wish to make the following comments.

THE oxime which is formed in the root nodules during the nitrogen fixation of legume bacteria1 has at last been isolated and characterized. The oxime precipitates according to Foreman's method, which fact already indicates it to be the oxime of a dicarbonic acid. Extracting the oxime with ether, we succeeded in preparing the copper salt from it. The analysis of this salt showed that the compound is the oxime of oxalacetic acid. Thus the formation of aspartic acid in the biological fixation of nitrogen via the oxime of oxalacetic acid has been finally confirmed.

ACCORDING to the present conception the keto-acids occupy a central position in the synthesis of amino-acids. Attention has been paid especially to the ‘fundamental keto-acids’, namely, oxaloacetic acid and keto-glutaric acid, since the amino group of aspartic and glutamic acids formed from them is transferred to other keto acids. In green plants, however, keto-acids other than oxaloacetic acid—the presence of which in the growing legumes has recently been demonstrated in this laboratory1—have hitherto not been found, evidently due to the absence of suitable methods.

IN this laboratory, fermentation of birch, aspen and pine-dusts has been investigated by enrichment cultures of thermophilic1, and recently also of mesophilic2, cellulose bacteria. he Tfiner the wood was ground, the more of the cellulose was fermented. In the best cases, a fermentation of about 70 per cent of cellulose in wood was obtained with the leaf-tree dust at 60° C. Distinct fermentation could be noted only a day after inoculation. Our results have thus disproved the earlier conception that the cellulose in wood is fermented only when lignin is in some way destroyed3, and are evidence against the supposition that cellulose and lignin are chemically bound in wood. Nevertheless there may be such a linkage, for the long cellulose molecules may be broken on grinding wood. If we presume that lignin is bound to the other end of the fibrous cellulose molecule, there would be formed from the free end of these molecules fragments which afford a suitable substrate for bacteria. As lignin is decomposed to some extent during fermentation (in one experiment with birch dust the decrease in the lignin content was 11·4 per cent, and in methoxyl content 29·2 per cent) the bonds between lignin and cellulose can also be broken, so that even the cellulose bound with lignin becomes fermentable. The assumption that a part of the cellulose in wood is bound with lignin, while a part is free, is in accord with our findings. This would also explain why the whole amount of the carbohydrates in wood-dust could not be fermented.

INCREASING attention has lately been paid to the composition of the protein constituents of the green plants. Important work has been done in this field, particularly by Chibnall and Wright. In the present letter we wish to direct attention to an important but rather neglected question in the study of the plant proteins. One of us (A. I. V.) has already referred to this question in the discussion on the chemistry of grass crops at the recent Norwich meeting of the British Association1.

LINKO and I1 isolated, last autumn, from Polygonatum officinale (and also from Convallaria majalis), a new imino-acid which on acid hydrolysis gave mostly homoserine. The elementary composition of the new compound corresponded to the formula (C4H7O2N)n and had [α]20D − 118.4° (in water). The compound had all its carboxyl groups free and contained no primary but only secondary amino-groups. Because the compound contained no double bonds, it must have a cyclic structure. A 4-membered ring containing an imino-group and a free carboxyl group linked to the ring could have satisfied the formula, but using the method of Wendt2 a molecular weight of approximately 300 was found, which is three times as high as that calculated for the simple molecule (six determinations in concentrations of 0.63–2.22 per cent in a non-polar solvent, the lactam of 4-amino-cyclo-hexane-carboxylic acid; calculated for (C4H7O2N)3, 303.3). On the basis of the molecular weight found, the compound seemed not to contain a simple 4-membered ring, even if all other known facts suggested this structure, but a corresponding ring three times as large and with three imino-groups in a ring to which three free carboxyl groups were linked. There was no other possibility of explaining the high molecular weight.