388 Miscellaneous Inielligencc. 



influence upon the rapidity of the movement, but very sensibly 

 affects its extent. 



Absence of light, during a certain time, completely destroys 

 the irritability of the plant. The change takes place more 

 rapidly when the temperature is elevated, than when low. The 

 return of the sun's influence readily restores the plant to its 

 irritable state. It appears, therefore, that it is by the action 

 of light, that the vital properties of vegetables are supported, 

 as it is by the action of oxygen, that those of animals are pre- 

 served ; consequently, etiolation is to the former, what asphyxia 

 is to the latter. — Jour, de Phys. xcv. 474. 



7. Vegetation in Atmospheres of different Densities. — The fol- 

 lowing experiments have been made by Professor Dobereiner of 

 Jena. Two glass vessels were procured, each of the capacity 

 of 320 cubic inches, two portions of barley were sown in por- 

 tions of the same earth, and moistened in the same degree, and 

 then placed one in each vessel. The air was now exhausted in 

 one, till reduced to the pressure of 14 inches of mercury, and 

 condensed in the other, until the pressure equalled 56 inches. 

 Germination took place in both nearly at the same time, and 

 the leaflets appeared of the same green tint ; but, at the end of 

 15 days, the following differences existed. The shoots in the 

 rarefied air were G inches in length, and from 9 to 10 inches 

 in the condensed air. The first were expanded and soft ; the 

 last rolled round the stem and solid. The first were wet on 

 their surface, and especially towards the extremities ; the last 

 were nearly drj'. " I am disposed," says M. Dobereiner " to 

 believe, that the diminution in the size of plants, as they rise 

 into higher regions on mountains, depends more on the diminution 

 of pressure than of heat. The phenomena of drops of water on 

 the leaves in the rarefied air, calls to my mind the relation of 

 a young Englishman, who, whilst passing through Spanish 

 America as a prisoner, remarked, that on the highest moun- 

 tains of the country, the trees continually transpired a quantity 

 of water, even in the dryest weather; the water falling sometimes 

 like rain." — Bib. Univ. xxii. 121. 



8. Fruit-Trees. — ^The growth of weeds round fruit-trees re- 

 cently transplanted does them much injury, and diminishes 

 their fruit in sixe and quality. Sonnini in his Bibliothfeque 

 Physico-economique states, that to prevent this, the Germans 

 spread on the ground, round the fresh transplanted trees, as far 

 as their roots extend, the refuse stalks of flax after the fibrous 

 part has been separated. This gives them surprising vigour. 

 No weed will gro.v under flax refuse, and the earth remains 

 fresh and loose. Old trees, treated in the same manner when 

 languishing in an orchard, will recover and push out vigorous 



