6 SOME RECENT RESEARCHES IN PLANT PHYSIOLOGY 



found that the action of leaf diastase upon solid starch 

 granules was often not very marked, especially when the 

 starch and diastase were obtained from the same plant. 

 Thus the first stages of the action on the starch granules 

 seem to be dependent upon the life of the protoplasm, or 

 the presence of an enzyme not easily extracted. To sum 

 up, however, it seems justifiable to conclude that the 

 diastase of the leaf is largely concerned in the dissolution of 

 starch for the four reasons which follow: (1) Diastase occurs 

 constantly and. abundantly in leaves. (2) Its amount 

 appears to depend upon the occurrence of starch. (3) Its 

 increase and decrease shows a remarkable periodicity. 

 (4) This periodicity is correlated with the appearance and 

 disappearance of starch. 



THE SUGARS or THE LEAF, WITH SPECIAL REFERENCE 

 TO TROPMOLVM MAJUS. 



IDENTIFICATION AND ESTIMATION OF LEAF SUGARS. 

 At the time when Brown and Morris began their researches 

 it was known from the work of Kayser (1883), A. Meyer 

 (1885), Schimper (1885), and Keim (1891), that reducing 

 sugars and a non-reducing sugar, cane-sugar (sucrose or 

 saccharose), existed in leaves. Estimations of these had 

 been made by means of Fehling's solution, which is reduced 

 by glucose, fructose, and maltose, but not by cane-sugar. 

 Meyer had also shown that leaves which contain little or 

 no starch, such as those of Iris germanica, Allium cepa, etc., 

 are relatively rich in sugars when compared with starch - 

 forming leaves. 



Brown and Morris selected the leaves of Tropceolum 

 majus as suitable for their object, to determine the up-grade 

 and down-grade products of assimilation, and to ascertain 

 the forms of sugar employed in translocation, respiration, 

 and cell growth. In this leaf they detected only the four 



