K. 8. Salmon 95 



plant a: leaf at 5tli node (from apex) bearing numerous "powdery" patches. 



,, 4th ,, bearing " hunips," showing a few very young sterile hyphae. 

 plant &: „ 5th ,, bearing numerous "powdery" patches. 



,, 4th ,, bearing " humps," showing a few young sterile hyphae. 

 plant c: ,, oth ,, bearing numerous "powdery" patches. 



,, 4th ,, bearing green "humps" which showed under a lens no 

 signs of any hyphae. 

 All the plants bore at the respective nodes two leaves, each with the mildew in the 

 same stage of development, and one leaf at each node was left unsprayed as a control. 

 The spraying (using an atomiser) was carried out on June 6. By June 10 it was 

 apparent that on all the sprayed leaves where the mildew had been in the "powdery" 

 conidial stage the ammonium sulphide solution had almost or quite killed the fungus ; 

 in every case, however, the leaves which bore the humps showed the mildew in a 

 further stage of development. On plant a there were numerous tiny tufts of conidio- 

 phores appearing from the "humps " ; on plant b there were two such tufts of conidio- 

 phores, and on plant c nine such tufts. By June 17 the original "powdery" patches 

 on the three sprayed leaves were all dead and in many cases semi-obliterated ; the 

 control leaves all bore very numerous almost continuous densely powdery patches. 

 The sprayed leaves with the "humps" were as follows: a, ten very small though 

 densely powdery tufts had developed over the "humps"; b, seven small densely 

 powdery tufts of conidiophores had developed where the youngest "humps" had 

 been, — where the "humps" had shown, at the time of spraying, mycelial hyphae, 

 the fungus had been killed ; c, twelve tiny powdery tufts of conidiophores had 

 developed over the "humps." In every case the control leaf showed much more 

 numerous and much larger densely powdery patches of conidiophores. It was clear 

 from this experiment that the ammonium sulphide solution used was fungicidal for 

 the mildew in the "powdery" conidial stage, but was not fungicidal for the mildew 

 in its earliest stages of development, although it appreciably checked its growth. 



In E.vper. 2 the fungicide used was the same concentrated solution of ammonium 

 sulphide diluted 1 to 50 with water (and containing 1 per cent, soft soap). The 

 seedling hop-plant used bore at the 5th node (from the apex) two leaves, each 

 bearing very numerous "powdery" patches of mildew, and at the 4th node two 

 leaves, each bearing from thii-ty to forty "humps," only a few of which showed 

 young rayceUal hyphae on their surface. One leaf at each node was sprayed on 

 June 6; the remaining leaves served as controls. On June 10 the "powdery" 

 patches on the sprayed leaf were all dead and semi-obliterated; the "humps" on 

 the sprayed leaf showed no signs of any living mildew. On June 12 the control leaf 

 at the 5th node bore numerous densely powdery patches, while the sprayed leaf 

 showed no signs of any living mildew; at the 4th node the sprayed leaf bore about 

 tliu'ty "humps" Avith no trace of mUdew developing from them, while the control 

 leaf bore over thii'ty "humps" each of which now bore a small densely powdery 

 patch of conidiophores. On June 20 the sprayed leaf at the 4th node was of a healthy 

 deep green colour and still showed the original "humps ' but no trace of mildew 

 occurred anywhere on the leaf ; a photograph of this leaf as it appeared at this date is 

 reproduced in Plate XV, fig. 1. The control leaf at the 4th node now bore densely 

 "powdery" patches covering over the original "humps"; a photograph of this leaf 

 is shown in Plate XV, fig. 2^. 



^ I am indebted to i\Ir H. Wormakl for taking these photooiapbs. 



