PRUSSIC ACID IN PLANTS 41 



of Hcvca brasilicnsis, 1 from which Para rubber is procured ; the 

 seeds, leaves, and flowers of numerous rosaceous plants, grown 

 either for the sake of their flowers or fruit ; the seeds of several 

 species of Vicia, 2 largely used as feeding-stuffs ; the leaves of 

 Ipomoca dissecta? used in the preparation of " noyau " ; and, 

 lastly, the leaves of the " great millet," Sorghum vulgare, 4 and of 

 maize, both widely cultivated for the sake of their edible grain. 



In all plants in which " cyanogenesis " has been thoroughly 

 investigated, it has been ascertained that the prussic acid occurs 

 for the most part not in a free state, but combined, usually in 

 the form of a glucoside. 



Comparatively little progress has been made till recently 

 in isolating and characterising these glucosides, which appear 

 to be the form in which prussic acid is temporarily stored by 

 plants in which cyanogenesis occurs, and still less work has 

 been done in characterising and classifying the enzymes, which 

 usually occur with the glucosides and possess the property of 

 decomposing them, thus generating prussic acid. Cyanogenesis 

 opens out in these two directions extensive fields of investi- 

 gation for the chemist. But the subject is probably of even 

 more interest to botanists, since Treub 5 has suggested, as the 

 result of his investigations of Pangium cdnle and Phaseolus 

 lunatus, that the formation of prussic acid is probably the 

 first step in the process by which these plants convert the 

 " inorganic " nitrogen of nitrates into the " organic " nitrogen 

 of proteids. 



Apart from these purely scientific aspects cyanogenesis is of 

 great, though perhaps rather grim, interest from the agricultural 

 point of view. One of the problems which every agricultural 

 department is sooner or later called upon to deal with is that of 

 plants poisonous to farm animals, and there is quite an extensive 

 literature on this subject scattered through the various agricul- 

 tural journals. 6 Recently several plants of this type obtained 

 from British colonies and dependencies have been examined at 

 the Imperial Institute, and it has been shown that their toxicity 

 is due to the formation of prussic acid when the plants are eaten 



1 Van Romburgh, Ann.jard. bot. Buitenzorg, 1899, 16, 1. 



2 Ritthausen and Kreusler, Journ. fier ftrakt. Chemie, 1870, 2, 2>33- 



3 Med. uit ''stands plantentuin, 1888, vol. 29. 



4 Dunstan and Henry, Phil. Trans. 1902, A. 199, 399. 



6 Ann.jard. bot. Buitenzorg, vol. 13, and series ii. 1905, 4, 86. 

 6 Maiden, Plants Poisonous to Stock. 



