106 ACTION OF LIGHT AND HEAT 



crable a part, as effectually to distinguish them from mere 

 brute matter ; but, in regard to the instinct and sensibility 

 of the vegetable creation, I fear we must abandon the sub- 

 ject to poets, who have often treated it with much beauty. 



The inclination of plants towards the light, we sober 

 minded botanists account for in a far less romantic manner. 



I must relate to you an experiment made by Mr. Tex- 

 ier, which shows that plants, far from being endowed with 

 feeling, are mechanically compelled, by their kind parent 

 Nature, to turn towards that quarter which is most con- 

 ducive to their well-being. Mr. Texier placed a plant 

 in a dark cellar, where it was supplied by openings on the 

 one side with light, and on the other with air ; and the 



flant was left at liberty to give the preference to either, 

 n a short time the point was decided : both leaves and 

 branches extended themselves towards the light. This 

 partiality may, perhaps, be thus explained. Those parts 

 of a plant most exposed to the light becoming harder and 

 less susceptible of elongation than the parts more in the 

 shade, the two sides being unequal, the one is obliged to 

 yield to the other; the soft, yielding, elongated side to 

 that which is harder and more contracted. If one side 

 of a branch is more elongated it will take a curved form, 

 as may be seen in the figure (Plate IV. fig. 5. ;) where 

 the dark line represents the accumulation of carbon and 

 contraction of growth, and the fine line, the softer tex- 

 ture and greater elongation ; and thus you see that the 

 plant mechanically assumes a position in which it may 

 receive the greatest benefit from an element so essential 

 to its welfare. 



Caroline. This is extremely curious ; and it accounts 

 for the tendency of plants towards the light in a manner 

 so simple and clear, that, mechanical as it is I cannot 

 doubt its correctness. 



Mrs. B. It has been suggested, that advantage might 

 be taken of this natural mode of curving wood for the 

 construction of ships, the ribs of which are bent by arti- 

 ficial means. Let us now proceed to examine the effect 

 of temperature on plants. 



Heat excites and accelerates the circulation of the jui- 



594. What experiment was made by Texier! 595. What was 

 the result 1 ? 596. How was this result explained! 597. How is it 

 illustrated by fig. 5, Plate IV. 1 598. What advantage does Mrs . B. 

 think might be taken of this in the growing of timber! 599. What 

 effect does heat have on the circulation of the juices of plants! 



