ox THE CHEMICAL ASPECTS OF CVANOGENESIS IN PLANTS. 153 



beans produced by the wild plant in Mauritius those wbidi were darkest 

 in colour yielded most prussic acid. This observation was confirmed by 

 Dunstan and Henry ' for beans produced from wild plants in Mauritius, 

 and subsequently it was found by these authors that the pale, buff- 

 coloured, semi-cultivated beans produced by Phaseolus lunatns in Burma 

 contained only traces of the glucoside, whilst the large white beans prO' 

 duced by careful cultivation of the plant in the South of France con- 

 tained none. These observations have been confirmed in a general way 

 by Guignard,'- Kohn-Abrest,^ and by Tatlock and Thomson,"* though 

 the first-mentioned author states that he also obtained traces of prussio 

 acid from the wliite beans produced by careful cultivation. He has, in 

 addition, shown that the relationship Letween the depth of colour and the 

 amount of prussic acid yielded by the beans produced by the wild plant 

 in Java is not so clearly marked as is the case with the beans produced in 

 Mauritius. 



2. By the ini^cstlyation of the dislributicn of cyanogenetic compounds 

 in the vegetable kingdom. — To this side of the work many investigators 

 have contributed, but reference may be made more especially to the 

 pioneer work done by GreshofF,"' and more recently by van Romburgh," 

 who have shown that prussic acid is produced by many plants occurring 

 in the Dutch East Indies. Investigations in this dii-ection have also been 

 made by Hebert,^ Jouck," Briinnich,^ and others. 



3. By chemical investigation of the ^^''ogrcss of cyanogenesis in 

 plants. — "Work of this kind has been done by Jorissen and Hairs ^'^ as 

 regards flax, by Joi-issen " and Marco Soave '- as regards the sweet 

 almond, by Briinnich '^ for a number of grasses cultivated in Queensland, 

 by Hubert,'^ and by Dunstan and Henry ''' for the various plants they 

 have investigated. 



The results of this work, taken generally, go to show that in cases 

 where there is little or no cyanogenetic glucoside in the .seed (e.g. Lotus 

 arabicus, the sweet almond, linseed, and sorghum) there is on germina- 

 tion a large and rapid increase in the total amount of prussic acid avail- 

 able. Thus whereas flax seed yields only 0-008 per cent, of prussic acid, 

 flax embryos four to five inches high yield as much as 0'135 percent. ; and, 

 similarly, whilst sweet almonds yield the merest traces of the acid, almond 

 embryos eight days old furnish as much as 004 per cent. Further, it 

 has been proved in the case of flax, sorghum, Lotus arabicus, and maize 

 that the percentage of pru.ssic acid available reaches a certain maximum, 

 and then diminishes, in some cases to zero. The stage at which this 

 maximum occurs varies with different plants. Thus in flax the percentage 

 of acid reaches the maximum when the embryos are about 45 inches 

 high. In Lotus arabicns the maximum is not attained until the plant 

 reaches the flowering stage ; in sorghum it occurs when the plants are 

 about twelve inches high, and in maize when they are about four 

 weeks old. Briinnich has also shown "' that with maize and sorghum 



> Proc. Hoy. Hoc, 190.3, 72, 285. = Cumpt. Hend., 1906, 142, 545. 



' Cuvipt. itend , 1906, 142, CSC. " Analyst, August 1900. 



^ Compare Dunstan and Henry, Compt. Rend., 1906. 



« Loc. eit. ' Jhill. Soe. Chim., 1896, iii. 15, 210, 



" Luc. eit. » Junrn. Chem. Hoc, 1803. 83, 783, 



"• Loc eit. " Ann. Agron. IBSfi, 10, 468. 



'• Ntioi-o Giorn. Bot. Ital, 1899, 6, 219. '^ Loc cii. 



" Ann. Aqron. 1898,416, '^ Loc eit. 



'» Ann. Agron. 1898, 416, 



