284 Philosophy of Blanching. 



No plant should therefore be left more than four hours ' 

 camphorated water, because the exciting action of the cam li ^ 

 when it is continued for a longer period, may do injury j n j 

 of good. It is not necessary to say that the final prospem 

 the plants, thus reanimated by the camphor-water, must / 

 pend upon their particular properties, the state of their r 

 and the care bestowed upon them. The camphor prod ! 

 no other effect than to restore to life plants nearly dead • aft 

 that, all proceeds according to the ordinary laws, and th i 

 ultimate state must be left to art and nature." 



PHILOSOPHY OF BLANCHING. 



Common Celery is a native of the meadows of many parts 

 of England, where it forms a rank, weedy, strong-smelling 

 herb, which is unfit for human food ; how different it is in oar- 

 dens every body knows. It is thought that its ceasin« to be 

 noxious when cultivated, is owing to the greater part of its 

 stems and leaves being blanched. No doubt you must be 

 curious to know why blanching a plant should destroy its un- 

 wholesomeness. In my last letter, I told you that the business 

 of leaves is to expose to light and air the sap they suck out of 

 the stem. The consequence of light and air acting upon the 

 surface of leaves, is the forming in their substance, which is 

 originally of the same yellowish white that you see in seeds, a 

 green color, which is more or less deep in proportion to the de- 

 gree in which the light is powerful ; thus a plant which stands 

 exposed to the sun all day long, has its leaves of a darker 

 green than another which grows among other trees, or near a 

 building which throws it into the shade for a part of the day; 

 and the latter again is darker green than a plant which grows 

 at the north side of a high wall, or in an enclosed court which 

 the sun's rays never enter. In like manner, if 3'ou cause a 

 plant, or any part of a plant, to grow in total darkness, it will 

 be entirely destitute of greenness ; or in other words, the sub- 

 stance of the plant will remain of its original yellowish white, 



