1906.] 



Cyanogenesis in Plants. 



153 



that the plants yielding the " bitter " and " sweet " cassavas are distinct 

 species, is most likely to be the correct one. 



The poisonous properties of the bitter manioc root seem to have been 

 known to the natives of Central and Southern America from very early 

 times and the process they use for preparing an edible meal from it seems to 

 be designed with a view to the complete elimination of the poison. The 

 process is described by Sagot* as follows : " The roots are scraped, peeled and 

 washed. This clean material is then rasped and the pulp left to ferment for 

 24 hours. It is then placed in a long flexible basket made of plaited rushes. 

 This is suspended by a handle at its open end and to the other a heavy 

 weight is attached by which means the pulp is compressed and a highly 

 poisonous juice oozes through the plaits. The pressed meal is taken out and 

 exposed for some time over a fire and then pounded, coarsely sifted, and 

 again exposed on a brass plate over a fire ; during this operation the meal is 

 constantly stirred so that it assumes a granular form." 



The same author states that : " Sweet cassava contains so small a quantity 

 of poisonous matter that the roots are cooked at a fire and eaten like 

 potatoes." 



Probably the earliest reference in European literature to the poison 

 contained in cassava root is that made by Clusius,f who says : " Ca§avi autem 

 panis est quo Indi tot seculis vitam sustentarunt et hodie etiam vescuntur 

 nostri Hispani. 



" Nee minore admiratione dignum est omnem Yucam X in continenti 

 nascentem tametsi quae ad S. Pominicum nascitur (ex qua Cacavi fit) similem 

 salutarem esse, ej usque fructum (radicem) edulem et succum inde manantem 

 potabilem, nullamque noxam adferre ; earn autem quae ad S. Dominicum 

 provenit (quacumque tandem ratione edatur) ej usque succum non coctum, 

 perimere. Locorum vero naturam tanti momenti esse ut quod salubre 

 alimentum in continenti praebet, id in omnibus insulis praesens fit venenum. 

 Quemadmodum Columella de Persico scribit, perniciosum venenum in Perside 

 fuisse, at ubi in Italiam translatum fuit noxium ilium succum deposuisse et 

 suavem salutaremque prsebuisse." 



This early observation of Clusius, that the generation of a poison in cassava 

 is associated with the conditions under which it is grown, is of special 

 interest in view of Wiley's statement that cassava cultivated in subtropical 

 countries, as distinct from the tropics, becomes much less toxic. § 



* Loc. cit. 



t ' Liber Exoticornm ' (Leyden, 1605), lib. 10, fol. 339. 



% Yuca is one of the vernacular names of the cassava plants and was in common use at 

 that time in the Spanish South American Colonies. 

 § ' Bull. U.S.A. Dept. Agric.,' Div. Chem., No. 44. 



