Scientific Intelligence. — Botany. 393 



est, are also those which least of all favour the act which causes 

 the development of the rudimentary organs of the grain. 2. 

 That, under the coloured rays of the highest illuminating power, 

 the radicles are developed least, and most slowly ; whilst, on 

 the contrary, the plumula? grow better, and more rapidly ; and 

 under the coloured rays of a weak illuminating power, the radi- 

 cles and plumulae take on a development similar to that which 

 they attained in the dark ; that, consequently, the growth in 

 length of vegetables under the rays erf' the prism is in the inverse 

 ratio of their illuminating power ; that, under all the coloured 

 rays, as in the dark, the radical hairs are developed towards the 

 aerial part of the radicle, a sure sign of the growth occasioned 

 by each of these circumstances ; that the lengthening of the 

 organs proceeds under the coloured rays as in the dark, and 

 that the different parts grow much quicker there than under the 

 influence of white light. 4. That the green colour of vegeta- 

 bles is developed much more rapidly under the influence of 

 compound light than under any ray whatever of decompounded 

 light ; that under all these rays, the parts on the vegetable des- 

 tined to become green, are yellow at first, then pass insensibly 

 to the palest green, then to the deepest tint under such rays as 

 enjoy the special property of suffering these changes to go on. 

 5. That these rays are on one side the yellow, and on the othfer 

 side the orange ; that the first possesses the 7naximum degree of 

 this property, and the second the minimum degree, the other 

 rays not at all producing the green colour; that the yellow ray 

 promotes the green colour in proportion as it is less intense, but 

 that it requires more time to produce greenness than would be 

 required in white light, and that it never can produce it in the 

 same degree as the latter. 6. It is, perhaps, allowable to state, 

 that this viridtjicating property of the rays in the spectrum 

 arises from their illuminating power, and it is immediately con- 

 nected with it ; but then, it must be acknowledged, that the 

 green ray itself does not possess the property at all, though it 

 shares with the yellow nearly in the maximum of illuminating 

 power. In concluding his letter, the author asks whether it is 

 solely by its splendour that light acts in the progressive colour- 

 ing of vegetables, all the organic elements of which, though 

 white at their formation, become subsequently covered with such 

 lively and diversified tints. — Annal des Scitfi. Nat* Oct. 1832. 



