288 BOTANICAL GAZETTE [APRIL 
seems to be attained at ordinary illumination. This seems to indicate that even 
the green areas of infected leaves are permanently immune to the variegation. 
Both in blue and in red light plants retained their variegation. 
Baur has extended his investigations to other variegated plants and 
finds that infectious chlorosis is of widespread occurrence. Both true variega- 
tion and the infectious form may occur in varieties of the same species. Among 
the forms investigated, a variety of Ligustrum vulgare L. and one of Laburnum 
vulgare (Griseb.) owed their variegation to infectious chlorosis similar to that of 
Abutilon Thompsont, Hort.—H. HASSELBRING. 
Hydrocyanic acid in plants.—GuvIGNARD has been giving special attention to 
plants which contain glucosides that produce this acid, and the conditions under 
which they may become poisonous. He relates in one paper’ the cases of poison- 
ing from the use of beans derived from wild or subspontaneous forms of Phase- 
olus lunatus L., a species having many forms, of which our Lima bean is one. 
In cultivation these are generally quite innocuous, but all contain phaseolunatin 
in greater or less quantity, which is split by emulsin into glucose, acetone, and 
hydrocyanic acid. The beans from Java have proved most virulent. A botani- 
cal and chemical history of the species is given, with illustrations of the seeds 
of many varieties. A new, convenient, and certain mode of detecting the acid 
is proposed. Filter paper is moistened with 1 per cent. picric acid and dried, 
then moistened with 10 per cent. sodium carbonate and dried, in which state it 
eeps its sensitiveness several months. A strip suspended in a test tube con- 
taining 0.02-0.05™s HCN becomes red-orange in 12-24 hours. 
In other papers* Guignard notes the presence of a cyanogenetic compound in 
ambucus nigra L., Ribes rubrum L., R. aureum Pursh., where it is found in the 
fresh leaves from vigorous shoots, green fruits, and young bark of the stem, while 
traces appear elsewhere. The compound is probably a glucoside that is split by 
emulsin, which accompanies it and does not seem to be a reserve food.° 
Emulsin he reports in the aerial roots of a considerable number of exotic and 
indigenous orchids,'° and also in certain yeasts't (resembling Sac. Pastorianus 
Hansen). This has also been announced by Henry and AULD." 
7 GUIGNARD, L., Le haricot & acide cyanhydrique (Phaseolus lunatus L.). Revue 
de Loic 1906. col. pl. 1. figs. 9. 
———,, Sur l’existence, dans le sureau noir d’un composé fournissant de 
oe cyan-hydrique. Bull. Sci. Pharmacol. 12 and 13. 1905-6. 
9 , Nouvelles observations sur le formation et les variations quantitatives 
du principe caliaitiielande de sureau noir. Idem. See also announcements in Compt. 
Rend. Acad. Sci. Paris June 3, July 24, Sept. 4, Dec. 26, 1905. 
7°, Quelques faits relatifs & V’/histoire de |’émulsine; existence générale 
de ce ferment chez l’Orchidées. L. c. footnote 8 
, Secretion d’émulsine par les levures. L. c. 
ta Proc. Roy. Soc. B. '76:568. 1905. 
