M. Wheldale 149 



Kraus(6) also found that some cut leaves redden when placed in 

 water in bright sunshine, and on analysis gave greater quantities of 

 aromatic substances than control leaves kept in the dark. 



Evidence for the Presence of Enzymes. 



If the formation of anthocyanin is dependent upon enzyme action, 

 it should be possible to obtain evidence of the existence of both 

 glucoside-splitting enzymes and oxidases in the tissues of anthocyanin 

 plants. 



Glucoside-splitting enzymes. For the detection of glucoside-splitting 

 enzymes I have employed the following method. The tissue to be 

 examined is well ground and thoroughly washed with 75°/^ alcohol: it 

 is then dried in air and extracted with distilled water. These processes 

 are carried out as far as possible under sterilised conditions. The 

 water extract is then added to a definite quantity of salicin solution 

 and kept, together with a control flask, at a temperature of from 

 36° — 40° C. for 24 hours. The following reaction then takes place : — 

 Salicin + water = saligenin + glucose. 

 The saligenin is extracted from the liquid by shaking with ether 

 and after evaporation of the ether its presence can be detected in the 

 residue by means of ferric chloride with which it gives a violet 

 colouration. 



By this method I have demonstrated the presence of a glucoside- 

 splitting enzyme in the following: — leaves of Corylus Avellana, Rumex 

 crispus, Taraxacum officinale and Primula sinensis, flowers of Gytisus 

 scoparius, Aquilegia vulgaris, Viola tricolor, Antirrhinum majus, 

 Primula sinensis, Narcissus pseudonarcissus, Cheiranthiis cheiri, Fritil- 

 laria imperialis, Polyanthus sp., Hellehorus orientalis, Pyrus japonica, 

 Prunus avium, Galanthus nivalis, Narcissus Tazetta, Pelargonium 

 zonule, and tubers of Solanum tuberosum. 



These results show that glucoside-splitting enzymes are widely 

 distributed. In other species a negative result was obtained but this 

 is to be expected, since all such enzymes may not be able to hydrolyse 

 salicin. 



If glucose solution is added to the salicin solution plus the enzyme 

 the hydrolysis of the salicin is greatly retarded. 



Also if the preliminary treatment with alcohol as described above is 

 omitted and a water extract is made from the fresh plant tissues and 

 added to salicin, very little or no hydrolysis of the latter takes place. 



