EFFECT OF LIGHT. 25 



structure ; and the decomposition of the carbonic 

 acid, the assimilation of the carbon, and the ex- 

 halation of oxygen, commences from the instant 

 that the rays of the sun strike them." Thus it 

 appears that though the food be collected in the 

 night (and hence the benefit of steaming in the 

 evening), light is necessary to its proper elabora- 

 tion and assimilation, — I am the more particular 

 on this matter from an error which frequently 

 occurs, in the supposition that these plants will 

 not bear exposure to the light — while it is evi- 

 dently as necessary to them as to other plants, 

 and during our long dull winters they cannot re- 

 ceive too much ; yet it must be borne in mind 

 that, being for the most part natives of the dense 

 forests of the tropic, a softened light will be re- 

 quired,in summer, when the direct and vivid rays 

 of the sun would be extremely injurious to them, 

 for w^hen exposed to its more immediate influ- 

 ences, they lose all that rich luxuriance for 

 which they are so remarkable, their leaves be- 

 come spotted with brown, in the form of blisters, 

 their progress is very much checked, and with 

 some species entirely suspended ; yet there are 

 some that will bear a strong light without injury, 

 but their leaves are of a more succulent nature, 

 and consequently of a firmer texture ; these are 

 of the Vandese tribe. 



