374 CHLOROPHYLLE. 



reproductive functions are, by another change in the 

 chemical operations going on within the vegetable 

 structure, to be called forth, it has been found that the 

 heat rays become in a remarkable manner effective. It 

 has also been observed that plants bend from the red, 

 or calorific rays, instead of towards them, as they are 

 found to do to every other ray of the spectrum. From 

 this we may argue that the influence of these rays is to 

 check the vegetation, and thus to ensure the perfection 

 of the reproductive processes. 



It has already been stated that we have the means of 

 separating, to a considerable extent, the three principles 

 which we discover in the sunbeam, from each other, by 

 the use of absorbent media. 



By a peculiar yellow glass we cut off the chemical 

 principle of the sunbeam, and admit the passage of the 

 luminous rays only LIGHT. 



By a cobalt blue glass we obstruct the light, but 

 allow the chemical agent to pass through freely, without, 

 indeed, any loss ACTINISM. 



By a glass coloured deep blood-red by oxide of gold 

 we obstruct the chemical principle and much of the 

 light, but such a medium is perfectly transparent to 

 HEAT. 



Therefore, this gives us the means of experimenting 

 with either of these principles, and of examining the 

 parts which they respectively play in the work of 

 organization. 



Some seeds being placed in the soil, in every respect 

 in their natural conditions, duly supplied with moisture, 

 and a uniform and proper temperature maintained, we 

 place above the soil the three media above named, and 

 allow one portion to be exposed to all the ordinary 

 influences of the solar rays. 



The result will be, that the seeds under the blue glass 

 will germinate long before those which are exposed to 

 the combined influences of the sunshine : a few of the 



