1881 FLASHING LIGHT ON PLANTS 119 



sensitive to light than others. I do not know 

 whether yon found any evidence of this. 



I have just found that this year again I have 

 heen too late in asking them to send me cuttings of 

 the vine for grafting. I did not know that the sap 

 in vines began to run so early. 



I remain ever yours, very sincerely and most 

 respectfully, GEQ j EOMANES 



From G. Darwin, Esq., to G. J. Romanes. 



Down : April 18, 1881. 



I am extremely glad of your success with the 

 flashing light. If plants are acted on by light, like 

 some of the lower animals, there is an additional 

 point of interest, as it seems to me, in your results. 

 Most botanists believe that light causes a plant to 

 bend to it in as direct a manner as light affects 

 nitrate of silver. 



I believe that it merely tells the plant to which 

 side to bend, and I see indications of this belief 

 prevailing even with Sachs. Now it might be 

 expected that light would act on a plant in some- 

 thing the same manner as on the lower animals. As 

 you are at work on this subject, I will call your 

 attention to another point. Wiesner, of Vienna (who 

 has lately published a good book on Heliotropism) 

 finds that an intermittent light during 20 m. produces 

 same effect as a continuous light of same brilliancy 

 during GO m. So that Van Tieghem, in the first part 

 of his book, which has just appeared, remarks, the 

 light during 40 m. out of the GO m. produced no effect. 



