278 Fungicidal Projjerties of Certain Spray-Fluids 



m 



portion of the concentrated solution was heated on a water-bath with 

 excess of powdered sulphur until no more dissolved, when the red liquid 

 was decanted and preserved. The polysulphide sulphur in this solution 

 was estimated by Chapin's nietliod. 



Commercial hme-sulphur solution contains about 25 grams per 100 

 c.cm. of polysulphide sulphur and thus gives 0-33 per cent, of polysul- 

 phide sulphur in a 1 in 75 dilution. The calcium polysulphide solution 

 was diluted to contain 0-33 per cent, of polysulphide sulphur. 



Experiment 43. Calcium poli/.sulphide (0-33 per cent, polysulphide 

 sulphur) and 1 per cent, calcium caseinate. The solution proved fungi- 

 cidal, the fungicidal effect being evident by the fourth day after spraying. 



The experiments described above tend to show that the only con- 

 stituent of lime-sulphur solution which has appreciable fungicidal power 

 (at the strength at which this solution is used in practice) is calcium 

 polysulphide. 



This result is in agreement with the previous work(i,i') with am- 

 monium polysulphide solutions. 



Summary. 



The following solutions were tested with respect to their fungicidal 

 properties towards the " powdery,"' conidial stage of S. Humuli on young 

 hop-leaves in the greenhouse : 



(1) Disodiuni arsenate, containing 0-096 per cent. AsjOj proved 

 fungicidal and killed also patches of leaf-cells underlying the mildew- 

 patches, but did not otherwise injure the leaf. A solution containing 

 0-02 per cent. AsgOg was fungicidal without killing any leaf-cells. 



(2) Trisodium arsenate containing 0-077 per cent. AS2O5 proved 

 fungicidal. 



(3) Dicalcium arsenate, containing 0-048 per cent. AS2O5 proved 

 fungicidal : containing 0-024 per cent. AsoOj the solution was apparently 

 just fungicidal, but with 0-01 per cent. AsgOj the solution was practically 

 non-fungicidal. 



(4) Tricalcium arsenate containing 0-076 per cent. AsgOg is fungi- 

 cidal; containing 0-02 per cent. AS2O5 it possesses some fungicidal value, 

 but with 0-OT per cent. As^Og it is practically non-fungicidal. 



(5) The following constituents of hme-sulphur wash proved non- 

 fungicidal: calcium sulphate, sulphite, thiosulphate, hydroxyhydro- 

 sulphide. 



(6) Calcium polysulphide, at a strength of 0-11 per cent., proved 

 fungicidal. 



