296 Physiologie. 



Dunstan, W. R. and Henry, T. A., Cyanogenesis in Plants, 

 Part. II; The Great Millet, Sorghum vulgare. (Proc. 

 Roy. Soc. Vol. LXX. No. 461. June 1902. p. 153.) 



This is an abstract of the continued researches of the 

 authors lipon this subject: a notice of Part. I, on Lotus arabicus, 

 is given in Bot. Centralbl., Bd. LXXXIX, p. 39. 



Young plants of Sorghum have proved fatal to animals 

 in consequence, as the authors find, of the formation of hydro- 

 cyanic acid. The formation of the acid is due to the action 

 of a hydrolytic enzyme, apparently identical with the emulsin 

 of bitter almonds, on a cyanogenetic glucoside which the authors 

 term dhurrin, derived from parahydroxymandelic nitrile by the 

 association of the residue of one molecule of dextrose, and 

 having the formula Ca Hn O7N. When hydrolysed by emulsin, 

 it is converted into parahydroxybenzaldehyde, dextrose, and 

 hydrocyanic acid; 



Cu H 17 7 N + H 2 = Ct Hg O2 -f C 6 H12 6 + HCN. 



Dhurrin differs from amygdalin and from lotusin in being 

 derived from dextrose and not from maitose. 



The authors intend to fully investigate the problems raised 

 by the occurrence of cyanogenetic glucosides in plants. They 

 are at present engaged in examining several other plants which 

 have furnished hydrocyanic acid, among them being Manihot 

 utlllssima, Linum usüatlssimum, Lotus australis and Phaseolus 

 lunatus. Vines. 



Farmer, J. B. and Chandler, S. E v On the lniluence of an 

 Excess of Carbon Dioxide in the Air on the Form 

 and Internal Structure of Plants. (Proc. Roy. Soc. 

 Vol. LXX. Aug. 1902. No. 464. p. 413—423.) 



The authors examined the folloving plants that had been 

 used in the experiments of Brown and Escombe (see pre- 

 vious notice) : Kalanchoe Welwitschil, Solanum atropurpureum, 

 Begonia gracilis, Impatiens platypetala and Fuchsla sp. 



They find that the effects upon the form and structure of 

 these plants of growing them in an atmosphere containing about 

 three and a half times the normal amount of CO2 (that is about 

 1 per 1000) are briefly as follows: 



1. The elongation of the internodes is checked; but the 

 period of growth is lengthened. 



2. The growth in surface of the leaves is early arrested. 



3. The absolute number of stomata per unit area of Ieaf 

 surface is considerably increased in consequence of 

 the smaller size of the epidermal cells: but the propor- 

 tion of stomata to epidermal cells is approximately the 

 same as in normal leaves. 



4. The structure of the leaves is not materially altered. 



5. The xylem of the stem is less perfectly developed. 



