1906.] 



Cyanogenesis in Plants. 



155 



" bitter " forms, yielded prussic acid. This investigator made a careful 

 search for amygdalin, but was unable to obtain evidence of the existence of 

 this or any similar glucoside in the roots. Peckolt obtained a number of 

 substances from cassava ; these were ill-defined bodies with the exception of 

 manihotin and manihotoxin, which were crystalline. The former is described 

 as melting at 160°, and somewhat resembling mannitol. It does not contain 

 nitrogen. 



Peckolt also stated that hydrocyanic acid does not exist in the roots until 

 these are withdrawn from the soil, and suggested that the acid is formed as 

 the result of atmospheric action. 



That the hydrocyanic acid does not wholly occur free in the leaves of the 

 cassava plant was observed by van Romburgh,* who, by macerating the 

 leaves in water, and distilling the resulting liquid, obtained a distillate 

 containing both acetone and hydrocyanic acid, and suggested that the hydro- 

 cyanic acid occurred partly combined with acetone and partly in the form 

 of a glucoside. 



Preliminary Experiments. 



The results of previous investigators on the whole tended to show either 

 that hydrocyanic acid existed in a free state in cassava roots, or that if it 

 were present in the form of a glucoside, the latter must be of a very 

 unstable character, and readily decomposed with the liberation of hydro- 

 cyanic acid. 



With a view to avoiding any risk of decomposition of the glucoside, we 

 endeavoured at first to import fresh cassava roots from the West Indies, 

 but it was found to be impossible to do this successfully, since the roots 

 decomposed to a considerable extent in transit. 



Recourse was then had to " bitter " cassava root, sliced in a fresh state 

 and dried in the sun, and it was found that by this means material fairly 

 rich in a cyanogenetic substance could be obtained. By preliminary 

 experiments with this material it was found that the rind of the bitter root 

 was much richer than the interior portion, and recently we have worked 

 only with the rind prepared by stripping it from the fresh root of bitter 

 cassava and drying it in the sun. 



The whole of the material used in the present investigation has been 

 obtained from the West Indies, and we are indebted to Sir D. Morris, 

 Imperial Commissioner for Agriculture in the West Indies, who enabled 

 us to obtain supplies in the first instance, and to Mr. Bovell, Superintendent 

 of the Botanic Station, Barbados, who kindly undertook the preparation 



* ' Annales du Jardin Botanique de Buitenzorg,' 1899, ii, vol, 16, p. 15. 



