BV JAMES M. PETRIE. 221 



plants growing in the Botanic Gardens, through the kindness 

 of the Director, Mr. J. H. Maiden, to whom my thanks are 

 due. 



Methods Used. 



i. Parts of plants were cut up and steeped in water at 40*^ 

 C. for 24 hours. 



(c/) Alone. 



(h) With addition of emulsin prepared from sweet al- 

 monds, or an aqueous extract of the emulsin. 



(r) With addition of 1 cc. of a 05 per cent, solution of 

 amygdalin, prepared by extraction from bitter almonds, and 

 recrystallisation. 



ii. Parts of plants were plasmolysed by the vapour of chlo- 

 roform. Guignard, and Mirande have shown that the vapour 

 penetrates the living cells, and incites the retraction of the 

 protoplasm, with the result that the cells are hnally killed. 

 There then takes place, an increased outward diffusion from 

 the interior of the tissues, of water containing the different 

 substances previously localised in the living plant : that is, a 

 diffusion of the glucoside and enzyme from their respective 

 cells. These substances are then free to react chemically, and 

 since the products are volatile, they can be recognised in the 

 vapour. 



iii. The method of identification of the vapour of hydrocy- 

 anic acid is the colour change of sodium picrate paper from 

 yellow to red. This test was first used by Professor Guignard, 

 who ascribed the change to a reduction of the picrate to isopur- 

 purate by the hydrocyanic acid. 



In the following table the plants are arranged in the order 

 of the botanical classification in the Flora Australiensis, and 

 the results are entered in three columns as positive and 

 negative. 



Col. i. — Plant tested alone with water, or chloroform: -I- 

 here indicates the existence of both a cyanogenetic glucoside, 

 and an emulsin-like ferment. 



