652 KANSAS CITY REVIEW OF SCIENCE. 



In former times it was believed that this would not take place in the presence 

 of direct sunlight. But this view is now generally rejected, as it is well known 

 that seeds frequently germinate while lying on the surface of the ground and ex- 

 posed to the full light of the Sun. But the probability is that even in this case 

 the germination principally takes place in the night, and that this does not dis- 

 prove the general theory that direct sunlight is detrimental to change. The 

 change that takes place in the substance of the seed during this process seems to 

 demand such an explanation. But while there is some doubt on this subject, 

 there is none whatever that certain rays of light do have a very important influ- 

 ence. 



About forty years ago Robert Hunt made extensive experiments to deter- 

 mine the influence of light on the germination and growth of plants. The conr- 

 clusions to which he was led so far as germination was concerned are : 



1. Light prevents the germination of seeds. 



2. Actinic, or chemical rays quicken germination. 



These views have been called in question by several able investigators. But 

 this seems to have grown out of the fact that sufficient attention has not been 

 given to the distinction between germination proper and plant-growth. But this 

 distinction is of capital importance as these different processes involve exactly 

 opposite principles and are attended and followed by entirely different phenomena.. 



In germination oxygen is imbibed and carbonic acid exhaled, while in plant- 

 growth carbonic acid is absorbed and oxygen exhaled. The conclusion at which 

 we arrive is that the chemical rays penetrating, as they do, the upper stratum of 

 the soil, while the luminous and calorific rays are cut off, determine the germi- 

 nation of the seed. As corroborative of the correctness of this view, as well as of 

 the wisdom of the adaptation of the laws of light to the demands of the vegetable 

 world, it is pertinent to remark that during the spring, when germination gener- 

 ally takes place, the actinic rays predominate, and during the summer, when wood- 

 growth is the chief desideratum, the luminous rays that exert the most potent in- 

 fluence in the development of this part of the plant, are in excess of the others, 

 while during the latter part of the season there is a preponderance of the calorific 

 rays which exert a capital influence in determining the physiological processes of 

 flowering and fructification. 



It is a well established fact that electricity exerts a very marked influence in 

 accelerating the growth of plants. In 1782 Dr. Marat found electrified seeds 

 germinated many days sooner than those not so treated but otherwise subjected 

 to the same conditions. These conclusions have been verified by many experi- 

 menters from that time on. It has even been found that seed that from age 

 would not grow at all under ordinary conditions, after being subjected to electric- 

 ity for some hours grew vigorously. Considerable light was thrown on this sub- 

 ject by Pouillet, who in 1825, proved that in the process of germination a nota- 

 ble, quantity of electricity is disengaged. It is claimed by some experimenters 

 that an electrified wire buried beneath growing plants or even stretched in the 

 air above them exerts a very strong influence in accelerating their growth. I 



