CALORIFIC INFLUENCE. 



375 



seeds will struggle into day under the red glass, but the 

 process of germination is entirely checked under the 

 yellow glass. Here we see that the chemical radiations 

 have quickened the chemical changes, and accelerated 

 the process, under the red glass, through which rays 

 having some peculiar chemical action pass ; the germi- 

 nating process, though checked, is not entirely stopped. 

 Whereas, it would appear that under the influences of 

 light which has been deprived of chemical power, this 

 conversion of the starch into gum and sugar, which 

 appears to be necessary, is entirely prevented. 



If the experiment is continued, it will be found that 

 under the blue glass the plants grow rapidly, but weakly ; 

 and that instead of producing leaves and wood they 

 consist chiefly of stalk, upon which will be seen here 

 and there some abortive attempts to form leaves. 

 When the process of germination has terminated, if the 

 young plant is brought under the yellow glass, it grows 

 most healthfully, and forms an abundance of wood, the 

 leaves having an unusually dark green colour, from the 

 formation of a large quantity of chlorophylle. Plants 

 do not, however, produce flowers with readiness under 

 this medium; but if, at the proper period, they are 

 brought under the red glass, the flowering and fruiting 

 processes are most effectively completed.* 



* The practical value of the discovery now described, will be 

 best understood from the following letter from Mr. Lawson, of 

 Edinburgh:- 



Edinburgh, 1, G-eorge the Fourth's Bridge, 

 Sept, 8, 1853. 



MY DEAR SIR, I am favoured with yours of the 5th, relative 

 to my practical experience in the effect of the chemical agency of 

 coloured media 011 the germination of seeds and the growth of 

 plants. 



I must first explain that it is our practice to test the germi- 

 nating powers of all seeds which come into our warehouses before 

 we send them out for sale ; and, of course, it is an object to dis- 

 cover, with as little delay as possible, the extent that the vital 



