70 Physiologie. 



enough to be estimated, Xanthophyll was not formed from pure 

 Chlorophyll in the presence of CO2 and water, but a yellowish 

 green substance having all the properties of phaeophytin. The 

 experimental evidence on which recent theories are based is, 

 therefore, still unsatisfactory. E. M. Delf. 



Kidd, F., The Controlling Influenae of Carbon Dioxide- 

 Part III. The retarding effect of carbon dioxide on 

 respiration. (Proc. Roy. Soc. LXXXIX. 612. p. 136-156. 1915.) 



A previous communication demonstrated the narcosis induced 

 in moist seeds by the action of carbon dioxide. The retarding 

 effect of carbon dioxide on respiration is now shewn to occur in 

 other plant tissues; the depressant action is not a permanent 

 effect if the concentration of the carbon dioxide causing it be 

 sufficiently diminished. Both aerobic and anaerobic respiration may 

 show retardation under the influence of carbon dioxide. and in 

 each case a quantitative relation exists between the concentration 

 of carbon dioxide and the consequent depression of the respiration. 

 The results of the experiments described support the theory that 

 anaerobic anc^ aerobic CO2 production are processes genetically 

 connected in normal respiration, and that the rate of the anae- 

 robic process acts as the limiting factor in normal respiration. If 

 respiration be considered as partly „floating" and as partly „proto- 

 plasmic", then it is the former only which is affected by the 

 retarding action of carbon dioxide. E. M. Delf. 



Stiles, W., On the Interpretation of the results of Water- 

 Culture Experiments. (Ann. Bot. XXX. p. 427-436. July 1916.) 



This paper is a discussion of the difficulties arising in the 

 Interpretation of the results of water-culture experiments. It is 

 shewn that growth is the resultant of many different processes, 

 and is dependent upon many different factors any one of which 

 may limit its rate. The supply of nutrient Clements in a water- 

 culture can act as a limiting factor to growth and no clear evi- 

 dence has yet been obtained that the concentration of the nutrient 

 Solution may itself be a limiting factor, as has been asserted by 

 Dr. Brenchley. The method of water cultures has doubtful 

 value in many physiological problems partly owing to the difficulty 

 of analysing the results, and partly owing to the difficulty in 

 Controlling even the particular factor under investigation. 



E. M. Delf. 



Willaman, J. J. and R. M. West. Notes on the hydrocyanic- 

 acid content of Sorghmri. {Journ. Agric. Research. IV. p. 179—185. 

 1915.) 

 The following points may be presented as a summary of these 



notes: 



1) When Sorghum is grown on poor, infertile soil, added nitrogen 

 may slightly increase the amount of hydrocyanic acid in the plant. 

 With a fertile soil and abundant nitrogen this effect may not be 

 produced. 



2) During the first three or four weeks of the plants life the 



