634 EXPERIMENT STATIOK RECORD. 



The mechanism of carbon assimilation, III, F. L. Usher and J. H. 

 Priestley {Proc. Roy. Soc. [London], Ser. B, S-} {1911), No. B 5G9, pp. 101-112, 

 pgs. 2). — In previous papers (E. S. R., 18, p. 540) the authors presented their 

 conclusions on investigations relating to carbon assimilation, some of which 

 have since been criticized. They have repeated their investigations, modifying 

 them to some extent, and in the present paper they discuss the initial stages of 

 the assimilation process without reference to the synthesis of sugar or starch. 



The previous conclusions are modified, the authors having abandoned the 

 idea of the exclusive localization of catalase in the chloroplasts and also the 

 dependence of the post-mortem bleaching of chlorophyll on the presence of 

 carbon dioxid. They believe now that they are justified in considering the 

 primary products of the photolysis of aqueous carbon dioxid to be formalde- 

 hyde and hydrogen peroxid, and that the evolution of oxygen is due to the 

 decomposition of the latter substance by catalase. Up to this point the process 

 is entirely nonvital and can be readily produced artificially. 



The relation of the odorous constituents of certain plants to plant metabo- 

 lism, F. Rabak {Jour. Amer. Chem. Soc, 33 {1911), No. 7, pj). t2.',2-12.',7).— 

 In an investigation on the odorous constituents of a number of species of plants, 

 the author has studied their relation to plant metabolism, and in general be- 

 lieves that the esters do not manifestly seem to be affected during the fruiting 

 of the plant. There does, however, appear to be a period in the growth and de- 

 velopment of plants when, with the assistance of certain favorable conditions, 

 the chemical processes in the plant transform some of the basal constituents into 

 esters and corresponding alcohols. The odorous constituents formed in plants 

 are believed to be simply products of excretion formed during the metabolism of 

 the plant and are of no further use to the plant, since they are not obviously 

 utilized for any special purpose other than possible means of protection against 

 insect enemies. 



A research on the orig'in of alkaloids in plants, G. Ciamician and C. Ra- 

 venna {Atti R. Accad. Lincei, Rend. CI. Sci. Fis., Mat. e Nat., 5. ser., 20 {1911), 

 I, No. 9, pp. 614-624). — In the experiments reported. Datura and tobacco were 

 inoculated with certain nitrogenous and nonnitrogenous substances, and the 

 resulting effects on the alkaloidal content were noted. The authors state that no 

 positively definite conclusions can be drawn from their experiments, but that 

 they indicate that the vegetable alkaloids are derived from the amido acids. 



On the direct guaiacura reaction given by plant extracts, Miss M. Wheldale 

 {Proc. Roy. ^oc. [London], Ser. B, S', {1911), No. B 569, pp. 121-12',).— lu the 

 literature dealing with oxidizing euzyms attention is drawn to the fact that the 

 juices of some plants change guaiacum tincture directly while others bring 

 about a bluing only on the addition of hydrogen peroxid. Various explanations 

 have been given to this fact, some claiming that the reduction is due to a sec- 

 ond enzym, oxygenase. Doubt, however, has been cast on the existence of such 

 an enzym, and the author has carried on experiments and found that the power 

 giving rise to direct guaiacum action in any plant is always accompanied by 

 another phenomena, i. e., the formation of brown or reddish-brown pigment 

 when the tissues are injured mechanically or are subjected to chloroform vapor. 



The author's observations have led to the conclusion that the direct action 

 given by the extracts of plants examined is due to the presence of pyrocatechin 

 in the tissue of the plants, which rapidly oxidizes on exposure to the air and 

 then acts as an organic peroxid, enabling the peroxidase, which is almost 

 universally present, to transfer oxygen to the guaiacum. The plants which 

 the author examined and which were not found to contain pyrocatechin did not 

 give the direct action. 



