The effects of Light on the Germination of Seeds. 541 



in some measure, to explain the popular notion that mush- 

 rooms, and plants of that variety, grow most abundantly 

 under the influence of bright moonlight. It has never yet 

 been found that any heat comes from the rays of the moon, 

 and the amount of chemical action which has been detected 

 has been very small: we must therefore regard the moon- 

 beams as consisting almost entirely of the luminous rays ; 

 the other active rays being, in all probability, absorbed by 

 the moon's surface. 



It is not at present in. our power to explain, in anything 

 like a satisfactory manner, the way in which the luminous 

 rays act in preventing germination. The changes which 

 take place in the process have been investigated by Saussure : 

 oxygen gas is consumed, and carbonic acid is evolved ; and 

 the volume of the latter is exactly equal to the volume of 

 the former. The grain weighs less after germination than it 

 did before, the loss of weight varying from one third to one 

 fifth. This loss, of course, depends on the combination of 

 its carbon with the oxygen absorbed, which is evolved as 

 carbonic acid. According to Proust, malted and unmalted 

 barley differs in the following respects : — 



This shows that the insoluble principle, hordein, is, in the 

 process of germination, converted into the soluble and nutri- 

 tive principles, starch, gum and sugar. We are therefore at 

 present left in considerable doubt. We can only suppose 

 that the luminous solar rays act, as indeed we find they do, 

 on many of the argentine preparations, in preventing those 

 chemical changes which depend upon the absorption of ox- 

 ygen. A like interference has been observed, by Sir John 

 Herschel, to be exerted by the extreme red rays of the 



