152 Drs. Dunstan, Henry, and Auld. [Apr. H> 



in Phaseolus lunatus seed and in flax seed. This enzyme is of the emulsin 

 type {i.e., it appears to hydrolyse /3-glucosides) and exhibits similar activities, 

 but it also presents certain well-marked differences from emulsin, which will 

 be the subject of further investigation. 



Cyanogenesis in Plants. 



Part V. — The Occurrence of Phaseolunatin in Cassava (Manihot 

 Aipi and Manihot utilissima). 



By Wyndham E. Dunstan, M.A., LL.D., F.E.S., T. A. Henry, D.Se, 

 Principal Assistant in the Scientific and Technical Department of the 

 Imperial Institute, and S. J. M. Auld, Ph.D. 



(Received April 11,— Read May 10, 1906.) 



The " sweet " and " bitter " cassava plants are indigenous to Southern and 

 Central America, whence they have been introduced, especially the sweet 

 variety, into almost all tropical countries and are now widely cultivated for 

 the sake of their edible starchy roots, which are used for the manufacture of 

 the various forms of cassava starch, of which tapioca is perhaps the best 

 known. 



The plants are known in their native habitat by a variety of vernacular 

 names of which only one, " manioc " or " mandioca," has come into general 

 use. The name " cassava " seems to be restricted in South America to the 

 flour or meal made from the roots, but outside South America this name has 

 come to be applied to the whole plant. 



There are many varieties of cassava plants in cultivation in the tropics, 

 but these all appear to belong to either the " bitter " or " sweet " forms. 

 These two forms were regarded by Pohl* as distinct species and were named 

 by him Manihot utilissima and Manihot Aipi respectively. 



By other botanists the " sweet " cassava is regarded as a variety or perhaps 

 a cultivated race of Manihot utilissima,^ whilst others take the view that 

 Pohl's Manihot Aipi is identical with Manihot palmata.% Colonel Prain, 

 Director of the Royal Gardens, Kew, whom we have consulted on this 

 point, is of opinion that on the evidence at present available, Pohl's view, 



* ' PL Bras. Ic.,' i, vol. 32, p. 24. 



t Compare Sagot, ' Bull. Soc. Bot. France,' 1872, vol. 18, p. 341. 



X 'Index Kewensis,' fasc. iii, p. 162 ; and Peckolt, 'Pharm. Bund.,' 1886, vol. 4, p. 57. 



