Phj'siologie. 59 



fluctuations in the opticall}' active impurities than in the sugars 

 themselves. These fluctuations occur more or less regularly during 

 the period of 24 hours, indicating a regulär Variation in the impu- 

 rities. Variations in the values for Saccharose obtained in the stalks 

 point to the fact that most likely at least two optically active sub- 

 stances are present at different tiraes of the day, one substance 

 causing lov^^ values for cane sugar, the other high values. 



After all due allowances have been made for the influence of 

 these impurities it seems justiliable from a consideration of all re- 

 sults to assume that dextrose and laevulose exist in the leaves and 

 stalks as invert sugar, travel in nearh* equal proportions to the 

 root and are there transformed into Saccharose. There is not suffi- 

 cient evidence for anj^ conclusion to be drawn as to the relative 

 value of dextrose for the nutrition and metabolism of the plant. All 

 such conclusions in the past are valueless because the analytical 

 methods at present existing do not give true values for these 

 sugars. W. E. Brenchlev. 



'&' 



Davis, W. A., A. J. Daish and G. C. Sawyer. S tu dies of 

 the formation and translocation of Carboh3^drates in 

 plant s. 1. The carbohydratesofthe Mangold lea f. (Journ. 

 Agric. Science. VIT. 3. p. 255-326. 1916.) 



An account is given of the work of various authors on the for- 

 mation of carbohydrates in the foliage leaves of plants, on their 

 translocation to the storage organs, and on the waj^ in which the 

 carbohydrates are finally broken dovt'n and utilised in subsequent 

 growth. 



Much of the earlier work was vitiated by the failure to ensure 

 that no change took place in the carbohydrates after the picking of 

 the leaf, before analyses were made. Special care has been taken 

 in these experiments to check enzyme action immediatelj^ the lea- 

 ves were picked. Samples were taken every two hours for a period 

 of twenty four hours three times during the growth of the crop. 

 The leaf material was treated immediately with boiling alcohol and 

 ammonia to destroy the enzymes and extract the sugars. Estima- 

 tions were made of cane sugar, maitose (by means of maltase-free 

 yeasts), starch (by taka-diastase) pentoses and pentosans. The lea- 

 ves, midribs and stalks were dealt with separately. The results are 

 expressed in the form of tables and graphs. 



In the mangold leaf starch is absent as soon as the roots begin 

 to develope so that the sugars formed in the leaf can be translocated 

 to it. Maltose is entirely absent from leaf, midribs and stalks at 

 all times and under all circumstances. During earl}?" stages of 

 growth Saccharose is present in the leaf tissue in excess of the 

 hexoses. Later on, when sugar is being stored in the root, the 

 hexoses predominate. In the midribs and stalks the hexoses always 

 predominate and vary very widely in amount at different times, 

 while the Saccharose remains practicalh^ constant. The predomi- 

 nance of hexoses becomes more and more marked as the season 

 advances. The proportion of Saccharose in the leaf tissue foUows 

 the temperature curve closeh^ during the daytime, but the propor- 

 tion of hexoses increases faster than the temperature. The view is 

 taken that Saccharose is the primary sugar formed in the leaf, and 

 that it is changed into hexoses for the purposes of translocation. 

 The hexose is reconverted into Saccharose in the roots for the pur- 



