182 Mr. E. H. Acton. The Assimilation of Carbon 



Not tested whether plant formed starch again under normal con- 

 ditions after experiment, as specimens used were accidentally mislaid 

 in laboratory. 



No. 3. — Experiments with Glucose {Starch-sugar) . 



Commercial "pure glucose," obtained from Messrs. Hopkin aud 

 Williams, of London, was used. 



A. It is well known* that cut branches of plants, leaves, &c, form 

 starch when supplied with solutions of glucose. I did not repeat 

 these experiments. 



B. Solutions supplied to the Boots. 



(1.) Solution used. 



Plants. 



Results. 



The culture solution 

 + 1 per cent, of 

 glucose 



Quercus robur 

 Cheiranthus Cheiri 

 Euphorbia helioscopia 

 Phaseolus vulgaris 

 Acer pseudoplatanus 



All contained starch at 

 the end of 4 days. 



(2.) Finding that starch was formed under these circumstances, I 

 commenced a new series of experiments, in order to observe whether 

 the plants were able to withdraw the whole of the glucose from 

 solutions, and how long a time was required for the tirst formation of 

 starch. As the young plants of Cheiranthus were growing most 

 vigorously at this time, I used them for this purpose. 



The first point was easily answered in the affirmative. Using the 

 previously mentioned culture solution (containing 1 per cent, of 

 glucose), such an amount was taken as to contain 3*57 grams of 

 glucose (about 400 c.c.) ; six plants of Cheiranthus Cheiri, with their 

 roots immersed in the solution, had completely absorbed all the 

 glucose at the end of five or six days. In another similar experiment, 

 I found that three plants of Acer pseudoplatanus absorbed 1'86 gram 

 of glucose in eight days, but a fungus mycelium was beginning to 

 form at the end of this time, which may have assisted in removing 

 the glucose. It was proved that all the glucose had disappeared from 

 the solutions by the usual methods of testing, viz., with Fehling's 

 solution, &c, &c. 



In regard to the second point, I never found any formation of 

 starch to occur with less than ten hours' exposure to light ; but it is 

 obvious that experiments of this kind are of very little value, as it is 

 not possible to determine to what extent the previous treatment to 

 deprive tissues of starch has affected the normal assimilation processes. 



* See Introduction. 



