TEANSACTIONS OF SECTION D, 697 



Further expevimeiits are in progress wbichwill deal with the fate of the nitro- 

 genous and fatty reserves, and further with the subsequent <?rowth of the pollen 

 tube and the way in which this latter structure is enabled to avail itself of the 

 nutritive materials among which it finds itself during its passage down the tissue 

 of the style. 



5. The Presence of a Dlastatic Ferment in Green Leaves. 

 By S. H. Vines, M.A., F.R.S. 



The author was led to investigate this point in consequence of the statement 

 recently made by Wortmann * that green leaves either do not contain any diastatic 

 ferment, or contain it in so minute a quantity that its physiological importance is 

 practically 7iil. Wortmann accounts for the well-known fact that starch is trans- 

 formed into sugar in green leaves by attributing the chemical change to the direct 

 action of the living protoplasm. 



The author's observations lead him to the quite contrary conclusion, viz., that 

 diastatic ferment is present (probably at all times) in green leaves ; and that its 

 physiological activity is so well marked that it appears superfluous to invoke, as 

 Wortmann does, the direct action of the protoplasm in the conversion of starch into 

 sugar in the living leaf. 



The authors method of experimentation consisted in mixing equal volumes of 

 leaf-extract and starch-solution ; and then, after the mixture had been allowed to 

 stand for some hours, volumetrically determining the amount of sugar present by 

 means of standard Fehling's solution. 



The leaf-extract was prepared by triturating leaves with distilled water (100 c.c. 

 of water to 100 grammes of leaves), and then at once pressing the mass through a 

 strainer. A turbid, more or less acid extract is thus obtained. In the earlier ex- 

 periments a filtered clear extract was prepared ; but filtration was abandoned, 

 for it was found that a clear extract was much less active than a turbid extract. 

 Probably Wortmann's negative results are to be mainly ascribed to the use of 

 filtered extract. 



The starch-solution was prepared by boiling starch with distilled water, in the 

 proportion of -o gramme of the former to 100 c.c. of the latter. The vessel was closed 

 with a plug of cotton-wool whilst the liquid was boiling, to prevent the access of 

 bacteria, and was allowed to cool for some hours; a certain amount of sediment 

 was deposited at the bottom of the vessel, but only the nearly clear supernatant 

 Hquid was used for experiment. The starch used appeared, on microscopical 

 examination, to consist of a mixture of wheat-starch with some potato-starch. 



The mixture of leaf-extract and starch-solution was usually allowed to stand all 

 night (about fourteen to sixteen hours). A sample of the leaf-extract, diluted to the 

 corresponding strength, was in all cases analysed for sugar,andin most cases a larger 

 or smaller amount of sugar was found to be present in it. In some cases a control 

 experiment was made in which the leaf-extract had been boiled before being mixed 

 with the starch-solution ; in these cases the amount of sugar ultimately determined 

 did not exceed that found to be originally present in the leaf-extract, thus show- 

 ing that the boiled extract had not aflected the starch. In others, again, thymol or 

 boracic acid (■'> percent.) was added to the mixture in order to prevent any possibility 

 of the interference of bacteria ; in these, the amount of sugar ultimately determined 

 was about the same as that in the simple mixture of leaf-extract and starch-solu- 

 tion alone, showing that the results obtained were not in any degree due to the 

 action of bacteria. The whole experiment was generally completed within twenty- 

 four hours, and the flasks containing the mixture were not artificially heated but 

 were kept on the laboratory table during the night whilst the action was pro- 

 ceeding. 



In his experiments AVortmann made use of the colour-reactions, given with 

 iodine by solutions of starch and dextrin, for the purpose of determining the 

 amount of action, if any, of the leaf-extract on the starch-solution. The author, 

 however, discarded this method altogether ; for, according to Wortmann's own 



' Bot. Zeitnng, 1890. 



