J12 ACTION OF LIGHT AND HEAT ON PLANTS. 



the plant dropsical by the accumulation of water; and aque- 

 ous plants, Mrs. B. has told us, are most liable to freeze. 



Mrs. B. Emily's expedient has been tried, but not 

 without danger of the consequences you deduce from it. 



Fleshy fruits, such as oranges, apples, and pears, re- 

 quiring a great quantity of sap to supply sustenance, oc- 

 casion a great absorption by the roots. These plants are, 

 consequently, particularly liable to injury from frost; and, 

 when thus endangered, it is a useful precaution to gather 

 the fruit, in order to secure the tree. In the south of 

 France, the oranges are gathered on the first appearance 

 of a frost ; and should this operation not be completed be- 

 fore the frost sets in, it frequently occurs that the side of 

 the tree on which the fruit remains is attacked by the frost, 

 whilst that on which it has been gathered escapes unin- 

 jured. 



Caroline. Then, in cases of such urgency, they should 

 begin by gathering the fruit on the north side of the tree, 

 as being most exposed to the cold. 



Emily. Some fruits, like the peach, are coated with a 

 soft down ; which, I suppose, answers the purpose of 

 warm clothing ? 



Mrs. B. Yes ; it is perhaps, even a better preservative 

 from the cold than the coatings of the epidermis. This 

 soft down encloses and confines the particles of air on the 

 surface of the fruit on which it grows. Air, you may re- 

 collect, is a very bad conductor of heat, and especially air 

 in a tranquil state ; that which is imprisoned by the down 

 affords, therefore, the most useful shelter to the plant. 



Emily. I have often experienced the advantage of a 

 precaution of this nature, by holding up my fur-tippet, 

 before my mouth when encountering a sharp frosty wind ; 

 the air, held captive by these slender threads, reposes 

 tranquilly in its downy prison, and becomes mild and 

 genial to breathe. 



Mrs. B. You must observe, also, that, during its cap- 

 tivity, it is tempered by the warmth of the breath you ex- 

 pire, before being inhaled by the lungs ; so that, in fact, 

 you breathe a tepid, instead of a frosty air. 



630. Why do oranges, apples and pears, readily freeze! 631. 

 What singular occurrence sometimes happens to orange trees in the south 

 of France! 632. Why is the down upon peaches a good preservative 

 against cold! 633. To what does Emily compare this! 634.-r- 

 How does the air thus held become tempered before it is breathed! 



