BV JAJIES jr. I'KTIUE. 455 



5 gius. of leaves re(iiurt'il the enzyme from 10 giiis. of aliiudul pnwiler. 'fhe 

 ratio of enzyme to ghieoside was not eonstant. 



D. On the existence of free liijilnici/aiiic acid in jilaiits. 



Xumeious attenn^ts have been made in tlie past by various investigators to 

 determine what they assumed to be the uncombiued portion of the hydrocyanic 

 acid in the planis. In most of these the methods used have been shown to be 

 faultj-. When boiling water or dilute acid is poured on a mass of leaves in a 

 flask the glucoside and enzyme, both being soluble, gre brought into contact with 

 one another, and some portion of the mass will remain at a temperature sulfi- 

 ciently low for enzyme action during at least a few seconds. In this initial period 

 enzymes are known to be exceedingly active, and so it happens that vmless special 

 precautions are taken some hydrocyanic acid will l)e liberated in most cases. 

 Since it is so difficult to destroy tlie enzyme in plant leaves in this manner, 

 other substances have been tried \\liose presence will prevent enzyme action. 

 The chief of these is tartaric acid . 



Method. — Leaves were powdered, water with a little tartaric acid added, and 

 the llask jilaced in the incubator, at 40° C, for 1 day. In some, the leaves were 

 allowed to fall from the gTinding mill into the tartaric acid solution, in others the 

 intact leaves were steeped in the solution for 5 minutes, tlien jint through the 

 mill in presence of excess of solution, and the powder received also iu tlie solu- 

 tion, ^laceration and distillation followed as previously described. 



Table D. 



.-ht/o/vsis ill />i-fse/icc' of iaiiarir ariif. 



HCN 

 No. Particular treatment. uigs. % 



Sam]ilr 11. 



16 

 .3,5 

 .36 



Saiui.lH III. ' 37 



Control -ivitlioiit tartaric acid 12o 



Macerated in 1 % soln. of tartaric acid 4(1 



5 % .. I 10 



Leaves steeped and ground in o % tartaric acid 

 soln., distilled direct for 2 hrs. 



Deductions from Table D. — The results given in the Table show that although 

 the amount of hydrocyanic acid obtained is considerably reduced (Nos. 35, 36) 

 when maceration takes place in presence of tartaric acid, yet this has not pre- 

 vented a certain degree of decomposition from taking place. It is only when tlie 

 leaves are kept in presence of tartaric acid during the whole of the crushing and 

 bruising of their tissues that enzyme action is entirely pi-evented (No. 37) . Any 

 free, uncomljined hydrocyanic acid, existing in the plant as such, would have 

 distilled over from the tartaric acid solutions. 



Therefore no uncombined hydrocyanic acid exists in the leaves of Hetern- 

 (leiidroii. 



E. The influence of chloroform on antoh/sis. 



In the preliminary testing of a plant for hydrocyanic acid the plasmolysis of 

 the tissues is iisually brought about by chloroform vapour. Chloroform is also 

 often used as a preservative of plants and their extracts against the formation of 

 moulds. Plants or extracts on which moulds have been allowed to grow are 



