-S7A' WILLIAM SIEMENS, F.R.S. 257 



inent upon the wheat, barley, and oats grown as above stated, but 

 still more evidence will probably be required before all doubt on 

 the subject can be allayed. 



I am aware that the great weight of the opinion of Dr. Darwin 

 goes in favour of the view that many plants, if not all of them, 

 require diurnal rest for their normal development. In his great 

 work on ' The Movements of Plants ' he deals in reality with 

 plant life, as it exists under the alternating influence of solar light 

 and darkness ; he investigates with astonishing precision and 

 minuteness their natural movements of circumnutation and 

 nightly or nyctitropic action, but does not extend his inquiries to 

 the conditions resulting from continuous light. He clearly proves 

 that nyctitropic action is instituted to protect the delicate leaf- 

 cells of plants from refrigeration by radiation into space, but 

 it does not follow, I would submit, that this protecting power 

 involves the necessity of the hurtful influence. May it not rather 

 be inferred from Dr. Darwin's investigations that the absence of 

 light during night-time involved a difficulty to plant life that had 

 to be met by special motor organs, which latter would perhaps be 

 gradually dispensed with by plants if exposed to continual light 

 for some years or generations. 



It is with great diffidence, and without wishing to generalise, 

 that I feel bound to state as the result of all my experiments, 

 extending now over two winters, that although periodic darkness 

 evidently favours growth in the sense of elongating the stalks of 

 plants, the continuous stimulus of light appears favourable for 

 healthy development at a greatly accelerated pace through all the 

 stages of the annual life of the plant, from the early leaf to the 

 ripened fruit. The latter is superior in size, in aroma, and in 

 colour to that produced by alternating light, and the resulting 

 seeds are not, at any rate, devoid of regerminating power. 

 Further experiments are necessary, I am aware, before it would be 

 safe to generalise, nor does this question of diurnal rest in any 

 way bear upon that of annual or winter rest, which probably most 

 plants, that are not so-called annuals, do require. 



The beneficial influence of the electric light has been very 

 manifest upon a banana palm, which at two periods of its exist- 

 ence viz. during its early growth and at the time of the fruit 

 development was placed (in February and March of 1880 and 



VOL. II. 8 



