OCTOBER. 481 



readily observable in the horse-chestnut and pear, the 

 latter of which, though the fruit is mostly green, has 

 often foliage of the most resplendent crimson or car- 

 mine. Again, the pallid yellow of the fading leaves 

 of the Laurel has surely nothing to do with its black 

 fruit ; and the foliage of the vine assumes the same 

 faint purple hue whether the fruit be black, purple, or 

 green. * MACAIKE PBJNSEP, after various experiments, 

 came to the conclusion that the foliage in autumn 

 ceased to evolve oxygen, which it usually does in the 

 daytime, when in a healthy state, but that it received 

 that gas from the air, by which an acid was formed, 

 tinging the foliage at first yellow and then red. ISTo 

 doubt that when the action of cold destroys the vital 

 functions of the leaf, it must of necessity cease to 

 evolve oxygen, but being thus in fact dead, it can 

 scarcely receive that vivifying agent within its struc- 

 ture ; but, as after falling, we perceive the leaves 

 stretched "dry and withered on the ground," in one 

 uniform brown tint, perhaps the oxygen may act ex- 

 ternally upon the epidermis to impart that hue to the 

 disrobing frondage. But whatever may be the primary 

 influence that affects the change of colour in the leaf, 

 its fall is the mechanical effect of gravity upon a dead 

 substance, now in fact isolated entirely from the 

 vitality of the compound polypoid structure to which 

 it is still attached. Thus in the stillest autumnal 

 morn, when the woods curtained in vapour, seem to 

 have settled into lethargic torpor, and the lightest 

 thistle-down pants for flight in vain as the first burst 

 of sunlight streams through the reeking mist, scatter- 

 ing jewelled colours upon a myriad host of dewdrops 

 and concentric studded webs, leaf after leaf drops 



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