1903.] Cijanogenesis in Plants. 285 



" Cyanogenesis in Plants. Part III. On Phaseolunatin, the Cyano- 

 genetic Glucoside of Phaseolus lunatus!' By WYNDHAM E, 

 DUNSTAN, M.A., F.RS., Director of the Imperial Institute, 

 South Kensington, and THOMAS A. HENKY, D.Sc... (Lond.). 

 Pceceived June 10, Read June 18, 1903. 



(From the Scientific Department of the Imperial Institute.) 



Phaseolus lunatus is an annual plant, probably indigenous to South 

 America, but now generally cultivated throughout the tropics, where 

 its edible bean is used as a vegetable. The plant presents much the 

 same appearance as the common French bean, but the flowers are 

 smaller and more numerous, whilst the pods are crescent-shaped and 

 contain only two or three seeds. The latter, according to Cordemoy,* 

 are violet in the wild state, light brown with violet hues or patches 

 when semi-cultivated, and white in the cultivated state. The beans 

 produced by the wild plant are known in Mauritius as Pois d'AcJiery, 

 those from the semi-cultivated plant as Pois Amer, whilst the cultivated 

 product is termed Pois Adam or Pois Portal, and in English-speaking 

 colonies Lima or Duffin beans. 



Whilst the white cultivated beans of Phaseolus lunatus have never 

 been known to be poisonous, the coloured beans as well as the plant 

 itself in the semi-wild state have frequently exhibited markedly 

 poisonous properties, and attention is directed to this difference between 

 the white and coloured seeds by Church. f 



The semi-cultivated plant grown in Mauritius, where it is utilised 

 as green manure and occasionally as cattle fodder, was examined in 

 1 900 by M. Boname, Director of the Agricultural Station at Mauritius, 

 in order to ascertain the cause of its poisonous action. The beans 

 were shown to furnish hydrocyanic acid when crushed and moistened 

 with water. | The hydrocyanic acid was found not to exist as such 

 in the plant, but to be in some state of combination, probably in the 

 form of a glucoside which, owing to the simultaneous occurrence in 

 the cells of the plant of a hydrolytic enzyme, underwent hydrolysis, 

 furnishing hydrocyanic acid as one product. No attempt, however, 

 was made by M. Boname to isolate the glucoside or enzyme, and only 

 indirect evidence of their existence was recorded on the analogy of the 

 bitter almond. Prussic acid was found to be produced by all parts of 

 the plant, though in greatest quantity by the seeds. 



The fresh plant was examined later by van Eomburgh, who showed 



* ' Flore de la Reunion,' 1895. 

 t ' Food-grains of India,' p. 155. 



' Rapport Annuel de la Station Agronomique,' 1900, p. 94. 

 ' Annales du Jardin Botanique de Buitenzorg,' Series II, vol. 1, p. 2. 

 VOL. LXXII. X 



