ON PLANTS. 105 



very agreeable to the palate in lettuces and endive when 

 eaten raw, and it becomes perfectly soft by cooking ; 

 whilst those parts of a vegetable in which the woody fibre 

 begins to be developed, by the deposition of carbon, af- 

 ter cooking remain tough and stringy. You must have 

 noticed this difference in every dish of cardoons and of 

 celery which is served at table : those parts from which 

 the light has been completely excluded are quite soft and 

 tender, whilst those ribs which have been partially ex- 

 posed to it, are more indurated and fibrous. 



It was supposed by the ancients, and, indeed, taught 

 by their great naturalist, Aristotle, that the verdure of 

 plants was developed by the atmosphere, and that it was 

 the exclusion of air which prevented the roots from as- 

 suming that color. 



Emily. What would be the consequence of depriving 

 a plant entirely of light ? 



Mrs. B. The leaves would become dropsical and fall 

 off: fresh leaves would, indeed, sprout ; but these, hav- 

 ing no power to decompose carbonic acid, would be com- 

 pletely etiolated. Deprived of carbon, and in a great 

 measure of the earthy matter deposited by evaporation, 

 the new shoots would be soft and feeble, but conside- 

 rably elongated by the absorption of fluid which they 

 have not power to throw off. 



Mr. Bonnet of Geneva cultivated some peas in a cel- 

 lar totally dark, and they were completely etiolated. 



Emily. Pray, can you tell me why plants turn their 

 leaves and flowers, and even stretch out their branches 

 towards that side on which the light predominates ? 



Mrs. B. Some have imagined that this preference re- 

 sulted from a sort of instinct ; others have gone so far as 

 to discover in it an indication of sensibility. 



Emily. I begin to take such an interest in plants, 

 since you have made me better acquainted with them, 

 Mrs. B., that I should be delighted to find they were 

 raised something above the mere passive mechanical 

 beings in which Nature carries on her chemical and phy- 

 sical process without their interference. 



Mrs. B. In all organised beings life plays so consid- 



589. What was supposed by Aristotle? 590. If plants were en- 

 tirely deprived of light what would be the consequence! 591. What 

 experiment was made by Bonnet'? 592. Why do flowers and leaves 

 turn towards the light! 593. What does Mrs. B. say of instinct and 

 sensibility as belonging to vegetable life! 



