ON THE INFLUENCE OF LIGHT ON SEEDS AND PLANTS. 79 



and next under the ruby, blue, and orange glasses (1, 3, and 5). Except 

 under the blue glass, these plants have all been marked by the extraordinary 

 length to which the stems of the cotyledons have grown, and the entire abs- 

 ence of the plumula. No true leaves forming, the cotyledons soon perish, 

 and the plant dies. Under the green glass (6) the process of germination 

 has been exceedingly slow, and the plants, particularly the cresses and 

 mignonette, have speedily died. 



Under the blue glass (5) alone has the process gone on healthfully to the 

 end, and although 1 have found a few instances of a perfect plant under the 

 yellow glass (4), it has not on any occasion yet endured to the formation of 

 a flower ; excepting the plants under the yellow and blue glasses (4- and 5), 

 all have been more or less etiolated. 



The most remarkable phsenomenon remains to be noticed ; under all ordi- 

 nary circumstances plants bepd towards the light, whereas those growing 

 under the red glass (2) have invariably bent from it. 



The experiments with the light analysed by the fluid media, have been in 

 every respect confirmatory of the results I originally obtained, which were 

 published more than two years since in the Philosophical Magazine. Ger- 

 mination has been in nearly all cases prevented by the absorptive powers of 

 yellow and red fluids (A and B). I say in nearly all cases, as I have within 

 the last few weeks, since the sun has shone with more than usual fervour, 

 noticed a few symptoms of weak germination under the yellow fluid (B). 

 It will be seen by reference to my paper above referred to, that I suspected 

 the difference in the results obtained by Professor Draper and myself, arose 

 from some peculiar difference between the condition of the rays of the sun 

 in Virginia and in England. The above fact confirms me in this opinion. 

 The absorptive powers of the atmosphere I have no doubt are constantly 

 changing, not merely with regard to its influence on the solar beam, but va- 

 rying as it regards particular rays ; and I think it will be found that the 

 condition of the prismatic spectrum is not on all occasions the same. I be- 

 lieve Sir David Brewster has proved this to be the case ; I am not, however, 

 acquainted with the facts. 



Under the green medium (C) the cotyledons only have been formed, and 

 these have all been etiolated. 



A very large wooden case was perforated with four small holes, two within 

 a few inches of each other, on either side of the front of the box, one pair being 

 about three feet from the other. These holes were covered with coloured 

 glasses, red (2), yellow (3), blue (5), green (6) ; thus arranged it was turned 

 over on the ground, several potatoes having been planted close to the back 

 of the box, at the greatest possible distance from the holes through which 

 alone light was admitted. 



The red and yellow glasses were at one end, and the blue and green at 

 the other. 



After some weeks, when examined, it was found that the shoots from the 

 potatoes, and the weeds which had sprung up from the ground, had, all of 

 them, in the most marked manner, run towards the yellow glass, through 

 which the greatest quantity of the luminous rays passed. This, I think, 

 proves that the luminous spectrum .has two distinct influences on the plant; 

 or otherwise, that its action is modified by some peculiar functions of the 

 plant itself. 



I submit these few results, incomplete as they are, to the attention of the 

 Association without any further remark. I do not consider that my experi- 

 ments have as yet proceeded far enough to warrant my taking up the time 

 of the Meeting with any opinion I may have formed. I hope the result of 



