AGKICULTUKAL IU)TANY. 541 



(Ijoxid iiiMV Ito (lo('()ini)oso(l Iiy nrnniuiii acctjilc tlic docdinpositioii i-cscnildiiif,' 

 tliiit \vliicli l.-ikcs i»liico witliin tlie plant. This is iuroiiipaiiicii i)y the foniiatioii 

 of foniialdcii.vdo. which is rapidly converted into some physiological inert suh- 

 stance, and i)ero.\id. which is decomposed with the evolution of {gaseous oxygen. 



Experiments on the mechanism of the evolution of oxygen from the green 

 plant suggest the presence of a catalyst, prohahly an enzym. and tliis en/,ym 

 has heen found in the foliage leaves of plants representing 4() natural orders of 

 vascular cryptograms and phanerogams. It also occurs in etiolated leaves and 

 potato tubers, appearing to be associated with amyloplasts, whether possessing 

 chl()roi)hyll or not. 



Experiments witli Spirogyra have shown that a starchless filament will con- 

 tain starch williin .". miiiulcs after exposure to light. ;ind it is helicved that 

 starch is not elaborated within the cell until the supply of that nutrient is in 

 excess of the cell's re(iuircments. It would therefore seem that there must be 

 some arrangement for the r.-ipid removal of formaldehyde, and for this reason 

 it is useless to attempt to find formaldehyde in healthy assimilating leaves. 



Snniniariziiig their conclusions, the authors state that ])hotolysis of carbon 

 ilioxid may take iiLic(> outside the plant in the absence of chlorophyll, i)roviding 

 one of the products is removed. The normal i)rodncts of photolysis are hydro- 

 gen jieroxid and formaldehyde, though under certain conditions formic acid 

 may be fnruied. In tlu' plant the decomposition of the hydrogen peroxid is 

 provided for by .a catalytic enzym of general occurrence, and the condensation 

 of the formaldehyde is dependent on the healthy condition of the protoplasm. 



In continuation of tlieir investigations, reported in the second ])aper. thi' 

 authors conclude that photolytic decomposition of aqueous carbon dioxid can 

 take jilace in the presence of chlorophyll independently of vital or enzym activity, 

 provided the necessary physical and chenucal conditions are strictly adhered to. 

 The products of the decomposition are formaldehyde and hydrogen peroxid, 

 formic acid being an intermediate product. It is possible to reconstruct the 

 process of photosynthesis outside the green plant, so far as the production of 

 formaldehyde and oxygen is concerned, by introducing a suitable catalytic 

 enzyni into the system, and for the production of oxygen and starch by intro- 

 ducing, in addition to the enzym. certain kinds of nonchlorophyll-bearing living 

 l)rotoi)lasm. 



There is direct experimental proof that formic acid is a product of the 

 photolytic de<'omposition of carbon dioxid in the i)resence of an inorganic 

 uranium salt. Formaldehyde has not been isolated and identified in the case 

 of decom|)osition by the inorganic uranium salt, but a study of the reactions 

 favors th(^ vi(>w that it is formed as a transitory intermediate iiruduct. 



Variations in chlorophyll assimilation under the influence of light and 

 temperature, W. Lubimenko (Coiiiiif. h'cinl. A((i<I. HcL [Paris]. 1)4 ilOOii), 

 .Vo. 11. iij). (JitO-Ull). — In continuation of previous investigations on the sensi- 

 tiveness of the chlorophyll of plants tolerant and intolerant to shade (E. S. R., 

 17. p. (J.")!), the author reports briefly on experiments to determine the effect of 

 light and heat on the decomposition of carbon dioxid by plants. 



In his experiments leaves of a number of sjiecies of tolerant and intolerant 

 trees were exposed for 15 minutes to full sunlight, the rays falling upon the 

 leaves i)arallel to their surface and at 4~>° and 90° angles of inclination. The 

 temi)eratures were held for different lots at 20°, 25°, 30°, 85°, and .'58° <'. and 

 the caibiin dioxid decomi)osition determined in each case. Among the i)lants 

 studied were lir. sjiruce. yew, and linden as tolerant species, and pine, black 

 locust, and wliit<' birch as intolerant to shade. 



20915— No. 6—07 .m i 



