2 54 GLUCOSIDES 



depletion is quite sudden, in others the glucosides gradually 

 disappear. On the other hand, in Indigofera and Samhuciis 

 the glucosides are not removed before the fall of the leaves. 



Treub also states that the amount present depends on the 

 quantity of available sugar ; he observed that there obtains 

 a daily variation, the maximum quantity occurring at about 

 midday. On the other hand, there is no consistent daily 

 fluctuation in Sorghum, and unhealthy plants may contain 

 more than healthy. It has also been ascertained that the 

 quantity of cyanogenetic glucosides in Pangium, Phaseolus 

 lunatus, Zea and Sorghum may be increased by the application 

 of manures rich in nitrates ; on the other hand, it must be 

 pointed out that in some cases, e.g. Phaseolus lunatus, the 

 glucoside may be ehminated from the seed by suitable methods 

 of cultivation. Also the amount varies in different varieties of 

 species, e.g. Sorghum. In some examples of seeds which con- 

 tain little or no hydrocyanic acid there may be a marked 

 increase on germination, thus in the flax, Dunstan and Henry * 

 found that the seeds contained -ooS per cent of the acid, 

 whereas in the seedhngs -135 per cent obtained; the same 

 increase also occurs in the sweet almond. Further, the 

 percentage of hydrocyanic acid in Linum, Sorghum, Lotus 

 arahicus and Zea Mais gradually increases to a maximum 

 and then decreases, sometimes to zero. 



The stage of development at which the maximum is reached 

 varies in the different plants ; thus, to take two extreme cases, 

 in the flax the maximum obtains when the seedlings are 

 between four and five inches high, whilst in Lotus arahicus the 

 maximum occurs at the period of flowering. 



It is clear that the actual amount of the substance in 

 question varies pretty considerably ; it may be very small or 

 relatively large, thus in the young leaves of Pangium the 

 presence of -3 per cent of hydrocyanic acid has been ascer- 

 tained. 



To summarize these observations : the amount of cyano- 

 genetic glucoside and the incidence of its maximum is very 



* Dunstan and Henry : " Brit. Assoc. Rep.," York, 1906 ; " Phil. 

 Trans. Roy. Soc. Lond.," 1901, B . 194, 515 ; " Proc Roy. Soc. Lond.," 

 B., 1900, 67, 224 ; 1901, 68, 374 ; 1903, 72, 285. 



