The effects of Light on the Germination of Seeds. 443 



Here we see that, contrary to what Ave might have supposed 

 at first, the highest temperature is not obtained behind the 

 red media, but behind those which have a yellow or orange 

 tint. Indeed, a higher temperature is obtained behind the 

 colorless fluid than any of the others ; and when we consider 

 that the thermic influence is not confined to the red spaces 

 of spectrum, but that it extends over all the visible rays, and 

 to a great extent below them, we see that a larger quantity 

 of radiant caloric must permeate the least colored media. 

 Red glasses and fluids absorb a larger quantity of the heat 

 rays than any other except black ones, and consequently 

 indicate a higher temperature themselves, although a lower 

 one is observed behind them. 



With these arrangements it was distinctly proved that, 

 under the influence of the luminous and calorific rays, ger- 

 mination was entirely prevented in many cases ; and in all, 

 the growth of the young plant was checked, and the devel- 

 opment of leaves and buds prevented. The following results 

 have been obtained with carefully selected roots of tulips and 

 ranunculuses : — 



The first appearance of germination took place with^he 

 tulips under the orange glass, (No. 3, of the prepared glasses,) 

 which was followed, in three days, by those under the red 

 glass, (2,) then by those under the ruby glass, (1,) aijd next 

 by those under the influence of the yellow glass, (4,) and 

 next under the blue glass, (5,) and then under the green 

 glass, (6.) The roots under the orange glass developed the 

 cotyledons a week earlier than those under the yellow, blue 

 and green glasses. But that the ranunculuses observed the 

 same relative order in germinating, I should have suspected 

 that some peculiarity in the bulbs had influenced the result, 

 although these had been selected with the most scrupulous 

 care. At first, the greatest progress was made by the tulips 

 under the yellow glass and orange glass, but the leaves under 

 each of these were by no means healthy, particularly under 

 the yellow glass, which had a singularly delicate appearance, 

 being of a very light green, and covered with a most delicate 

 white bloom. 



