294 KECOKD OF CDREENT RESEARCHES RELATING TO 



Dr. Siemens promises a more extended series of experiments, and, 

 in an article in 'Nature,'* the writer points out that to give the 

 matter a complete trial, it would certainly be desirable to compare 

 the results during longer periods of growth when the plants were 

 more thoroughly thrown on their own resources. It must be remem- 

 bered that seedlings grow to a large extent at the expense of the 

 materials stored up in the seeds, and the same thing is true of the 

 foliage produced from fleshy roots like those of the carrot. In both 

 cases the plant is mainly feeding on itself. The real test would be 

 to take some short-lived annual and see if it would run through its 

 course with illumination from an artificial source alone, and how the 

 actual weight of plant-tissue manufactured would compare with that 

 produced under an equivalent exposure to sunlight. The scientific 

 interest of the present application of the electric light must rest 

 mainly on the fact that the cycle of the transformation of energy 

 engaged in plant life is now complete, and that, starting from the 

 energy stored up in vegetable fuel, we can run through the changes 

 from heat to electricity, and thence to light, which we now know we 

 can store up in vegetable fuel again. 



Decomposition of Carbonic Acid by Leaves illuminated by 

 Artificial Light.t — Experiments on this subject by MM. P. P. Dehe- 

 rain and P. L. Maquenne have led to the following conclusions : — 



1. Leaves placed in tubes immersed in water and kept at a small 

 distance from the source of light, decompose carbonic acid when 

 exj)osed to the action of the Drummond light. 



2. They also decompose carbonic acid, but less powerfully, when 

 illuminated by the Bourbouze lamp. 



3. When the leaves are protected by a stratum of water decom- 

 position always takes place. When enveloped in benzine, which is 

 much more diathermanous than water, the decomposition is more 

 perceptible under the influence of the Drummond light ; while under 

 the influence of the Bourbouze lamp it is less perceptible, and the 

 opposite phenomena of absorption of oxygen and emission of carbonic 

 acid may be observed. 



The amount of light emitted by the Drummond light and the 

 Bourbouze lamp respectively was estimated in the former at 71, in 

 the latter at 62 candles. 



Distribution of Water in the Plant.J — G. Kraus has carried on 

 a series of investigations as to the relative amount of water in different 

 parts of the plant, and its influence on various vital processes. For 

 the purpose of the experiments the part of the plant, either entire or 

 dissected, was dried in porcelain or platinum vessels placed in copper 

 chambers at a uniform temperature of 110°-120° C. 



With regard to the distribution of water in the growing nodes and 

 internodes, the result attained was that an increase in the percentage 



* ' Nature,' xxi. (18S0) p. 438. 

 t ' Aim. Sci. Nat.,' L\. (1879) p. 47. 



X ' Festschr. Feier hundertjiilir. Bestehens Naturforsch. Gesell. Halle,' 1879, 

 p. 187 ; see ' Naturforscher,' xii. (1879) p. 439. 



