rort| CURRENT LITERATURE 475 
by reaction in more than half the roots, and relaxation index by reaction in 
fewer than half. The accompanying table from the article summarizes the 
results: 
Presentation Critical | Reaction Relaxation 
time time time index 
Lepidium sativum at 57—1eC, fs % min. 6 min. 25.5 min. 30 
25-27C. ieee Bay ae nak 40 
Lupinus albus at‘i7-18C. |}. 8.5..." ce Bley 46,5." 20 
of e Sige-g7C | e.g ae 23:0 5" 25 
One is struck here by the time demanded for relaxation from an exposure; 
it is very much greater than reported by Firrinc. The author attempted, 
without full success, to develop a formula by which any one of the critical 
periods can be calculated from the other three.—WiLLIAM CROCKER. 
otosynthesis.—LUBIMENKO™ finds that there is a light optimum for 
the production of dry substance by green plants. The absolute value of this 
optimum is less than that by which the chlorophyll apparatus is able to fur- 
nish the maximum of photochemical work expressed in the decomposition of 
CO.. By means of monochromatic filters and gasometric ‘determinations, a 
comparison is made of the action of the different colored rays on the decompo- 
sition of CO. These results are compared with the action of the same rays 
on the production of total dry weight. The energy for CO, decomposition 
in colored light depends upon the absorption of the various colored rays by 
the chloroplasts as well as on their caloric energy. The author objects to the 
method employed by Kniep and MINDER and others in determining the 
influence of different colored rays on CO, assimilation, on the ground that 
they measured the quantity of light falling upon the leaf and not that absorbed 
by the chloroplasts. The real carbon fixation expressed by the increase in 
dry weight is influenced unequally by the different colored rays. The maxi- 
mum increase in dry weight occurs under the action of the blue-violet rays. 
The yellow-orange rays are inferior to the red rays, and the minimum occurs 
in the green rays. It is necessary to assume two successive stages in the 
photosynthetic process. The first is characterized by the decomposition of 
CO, and synthesis of the first organic product. In this stage of the process 
the plant utilizes predominantly the energy of the red rays of the solar spec- 
trum. The second stage is characterized by the definitive fixation of the 
first organic product, and the plant employs for this work especially the blue- 
violet rays—Cuas. O. APPLEMAN. 
' LUBIMENKO, M. W., L’assimilation chlorophyllienne et la production de 
substance seche 4 la lumiére blanche et A la lumiére colorée. Rev. Gén. Bot. 2321-14. 
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