450 c \ A.\(MiK.\KSIS IN PLANTS, 



(2) The plant -powiler, with suffieient water to cover, was phu-cd iu two test- 

 tubes. («) was kept at 40° C. for 1 liour; {h) was boiled for 5 minutes and also 

 kept at 40° for 1 hour, the test i>aper used in eaeh. The result showed in (a) a 

 colour cliange to deep red within a minute, and in (h) no colour reaction after "24 

 hours, (c). To the tube ib) was then added a small speck of emulsin powder 

 prepared from sweet almonds, and the mass again digested at 40° (". After a 

 few minutes the test-paper showed a deep red colour. 



These experiments were done also witli aqueous extracts from the plant, tlie 

 boiled solutions yielding no hydrocyanic acid till emulsin was added. 



The plant therefore contains a g-lucoside and an enzyme, the latter being al)le 

 to decompose the glucpside with liberation of hydrocyanic acid, umler conditions 

 favouring enzyme action. The glncoside is also decomposed by the emulsin of 

 alniduds. 



CVAXOGKXKTIC Pr.AXTS OF THE b'AillLY SAPIXDACEAK. 



In the chemical literature of the cyanogenesis in jdants there already exist- 

 the records of six i^lants of the family Sapiiidacrae in which hydrocyanic acid has 

 been obtained. These are: — 



Alectryon excelsum Gaertn.. a Xcw Zealand tree (Greshoff). 



Alectryon tomentoaus b'adlk., a native Xcw South Wales tree (Smith and 

 Whit«). 



Alectryon coriaceiis Hadlk., ibid. 



Cupania sp^j. (Greshoff) . 



Schleiehera trijttga Willd., an East Indian plant. 



Ungnadia speeinsa Endl., a Mexico and Texas tree (Cheel and Penfold). 

 Heterodendron oleaefolia added to this list makes the seventh cyanogenetic plant 

 of the Sapindaceue. 



The only other existing species, B. diverfifolia, has been tested by the writer 

 in specimens from New South Wales and Queensland, but has always u-iven nega- 

 tixe results, showing the absence of any cyanogenetic compound. 



ESTIIIATIOX OF THE HtdROCYAXIC ACID. 



Many diflieulties were met with in attemjiting to determine the true amount 

 of hydrocyanic acid which this [ihiiit is capable of evolving under special cir- 

 cumstances. 



The enzymes characteristic of the various cyanogenetic plants are known to 

 act differently in most cases, especially as to their relative \elocities and the 

 position of the equilibrium point. These jdants also contain substances which 

 act as inhil)iting factors during the hydrolysis of the glucoside. that is, which 

 oppose its decomposition. There are likewise present certain bodies whose in- 

 fluence tends to recombine the ])roducts of hydrolysis and thus decrease the 

 amount of hydrocyanic acid available for estimation. 



When the leaves of fresh i)lants are macerated in water, there is no doubt 

 that their protoplasm continues its ])hysiological function for some time, and 

 utilises part of the liberated hydrocyanic acid in the synthetic processes of meta- 

 bolism. Although in a few cases it has l)een shown that the same glucoside 

 occui-s in certain widely different ])lants, such as phaseolunatin in Beans and 

 Flax seeds, gynocardin iu Panfjium- edide and Ofiiiocardia nditnilu. the great 

 majority of the cyanogenetic ))lants probably contain different glucosides. In 

 artificial hydrolysis such as with mineral acids, etc.. these glucosides behave dif- 

 ferentlv towards the hvdrolvsiiig agent. 



