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may be blanched by excluding them from this agent. Lettuces, endive, celery, 

 kale, and other vegetables, are prepared for the table by preventing the access of 

 light, as in the operations of tying up the leaves, earthing the roots, or covering 

 the whole plant with opaque earthen pots. The bleached pallid appearance of 

 greenhouse plants which have been kept in situations where the light has not been 

 sufficiently admitted, arises, also, from the same cause ; while the brilliancy and in- 

 tensity of the colours of flowers in tropical and alpine countries is owing to the in- 

 tensity of the light and the clearness of the atmosphere in such situations. Expo- 

 sure to light, therefore, tends to develop the colours of plants ; but in what way the 

 effect is produced is not so evident. Whether it arises from any chemical change 

 in the state of oxydation, or from any physical variation in the optical properties of 

 the vegetable tissues from their more vigorous growth and nutrition when under 

 the stimulus of this powerful and pervading influence, does not seem clear. The 

 green parts of plants, especially the leaves, exhale oxygen, as is well known, on 

 exposure to the light of the sun ; while the coloured parts, such as the flowers, 

 more frequently exhale hydrogen and azote. By the action of alkalies, also, the 

 red colour of many flowers becomes, in succession, blue, green, and ultimately 

 even yellow — a change which may possibly be owing to their acting as deoxydiz- 

 ing principles. The change in the blossoms of the Myosotis versicolor is from 

 yellow to blue, and ultimately to faded purple or red — that is under exposure to 

 the light, which, as it induces the exhalation of hydrogen and azote from the 

 coloured parts, tends, therefore to the accumulation of oxygen in the same parts, 

 the yellow passes successively into blue and a faded purple or pink. I have, how- 

 ever, never observed any approach to the intermediate stage of green between the 

 yellow and the blue flowerets of M. versicolor. The investigation of the 

 causes to which the colours of flowers are owing is very important, both in relation 

 to vegetable physiology and to optics ; and this little plant seems well calculated, 

 when submitted to judicious experiments, to afford valuable information to the in- 

 quirer into these interesting arcana of natural and physical science. 



Boa Constrictors. — A recent traveller in South America, journeying from 

 Lima to Vara, in the Brazils, observed that the inhabitants of the latter place take 

 great pleasure in rearing the Boa Constrictor (quere Python Tigris) ; and that 

 Mr. Smith, the North American consul, possesses several for the purpose of de- 

 stroying Rats, with which those parts are terribly infested. These creatures 

 sometimes attain the length of eighteen feet, and the colours of their skin are bril- 

 liant beyond description, particularly after moulting. They have never been 

 known to injure any one, and even exhibit local attachment to places and persons. 



