GEEEN VITRIOL. 183 



Peronospora viticola, De By. (mildew of the vine). — According to 

 Wuthrich the spores the most sensitive to green vitriol are those of 

 Peronosjiora. A solution of 00139 per cent kills the conidia after 

 fifteen hours' immersion. The first trials to combat mildew were made 

 in 1882. Millardet recommended a mixture of 4 lb. of green vitriol 

 in powder, 20 lb. of green vitriol, and 20 lb. of plaster. A nursery of 

 2000 Jacquez attacked with mildew in the middle of June was treated 

 2 July in dry and hot weather. Success was complete ; the young 

 buds had not suffered, and they resisted the re-invasion of September. 

 Eeich found that the treatment for anthracnose is also a preventive of 

 mildew. This treatment which consists in coating the stocks with a 

 25-50 per cent solution of green vitriol before the buds begin to unfold 

 is used with success at Armeilliere against the Peronosjyora. This 

 treatment is not always followed by the desired effect. 



Ustilago (smut) and Tilletia (bunt). — Green vitriol has no action 

 on the spores of Tilletia Levis (Kuhn). Wuthrich showed by labora- 

 tory tests that a 1-39 per cent solution of green vitriol hinders the 

 development of the spores of Ustilago, and a 13-9 per cent solution 

 kills them. The trials of Boiret made by sowing the spores of brown 

 rust on object glasses placed in a moist chamber at 18°-20'' C. 

 gave analogous results. A certain number of spores still germinate 

 after an hour's immersion in a 5 per cent solution of green vitriol or 

 after four hours' immersion in a 2 per cent solution, whilst the spores 

 do not germinate in a 0-5 per cent solution of blue vitriol. Green vitriol 

 has, however, been used for a long time to disinfect seed corn against 

 smut and bunt. A 2-5 per cent solution of green vitriol was used 

 in which the seeds were left to macerate for six to twelve hours, after 

 which they were limed, then left to dry in the air. The results ob- 

 tained were not very satisfactory. Mathieu de Dombasle artificially 

 infected a portion of grain by agitation in a sack with the dust of brown 

 rust, then he treated the infected grain with green vitriol, blue vitriol, 

 and lime. After sowing he got the following results : — 



TABLE XXIII. — Showing the Results of the Experiments of De Dombasle on 

 the Disinfection by Green Vitriol of Seed-Corn Artificially Infected on 

 Purpose. 



