492 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



disease. Keep the plants clean of yellow, dead, or dying leaves, being 

 careful to destroy them after removing them from the plants. Keep the 

 plants free from insects and other animal pests. Give careful attention 

 to ventilating, heating, and shading the frames, and also to watering, 

 cleaning, and cultivating the plants. Renew the soil each season before 

 setting the young plants by removing eight to twelve inches of the surface 

 soil and replacing it with that freshly prepared. Set the young plants 

 early in the spring in the beds where they are to remain for the season, 

 so that they may get well established before the hot dry weather of 

 summer makes its appearance. 



FURTHER REPORT ON VIOLET LEAVES. 



By Dr. Cooke, M.A. 



On the first occasion there was a large supply of leaves, but only the 

 smaller portion of them exhibited pale orbicular spots. On no other part 

 of leaves or petioles could I find any evidence of fungus disease. I 

 devoted three or four hours to close microscopic examination of the pale 

 spots, because I was convinced that the subject was one of great import- 

 ance, yet the dead tissue of the spots showed no mycelium which I could 

 detect. Certainly on none of them was there any evidence of hyphae, or 

 external threads. The second parcel of leaves was also ample, and on a 

 few of the oldest spots I found a little mycelium. I retained but half a 

 dozen leaves when the parcel was shown at the Scientific Committee. 

 Some two or three of the spotted leaves I kept nearly a week upon damp 

 flannel under a bell-glass. At the end I found upon the spots an ample 

 crop of the threads and conidia in all stages of an ordinary Cladosjwrium, 

 such as CladoHporuiin epiphyllum. Although I searched diligently I 

 could find no conidia of Cercospora Violce, which has just such spots. 

 Neirly all the species of Cladosporium are saprophytes, and in this 

 instance I am under the imjDression that the Cladosporium had nothing 

 to do with the original spotting, and that the presence of hypha* and 

 conidia was not manifest until after the discoloured spots, being quite dead 

 tissue, were subjected to a damp atmosphere. 



The report of the American spot disease, which is referred to Alternaria 

 Violce, states distinctly that the spots were present in most instances, with 

 no trace of mycelium or hyphse, and did not exhibit either until the leaves 

 had been kept in a damp atmosphere for many hours. This seems to be 

 precisely what happens with this British violet disease. The spots are 

 just like those of the American disease, and are just as barren of mycelium, 

 hyph», or spores. The Alternaria spores were only found after the leaves 

 had been placed under new conditions. Nevertheless subsequent cultures 

 seem to indicate that sowing healthy leases with the spores of Alternaria 

 produced the pale spots. 



It is strange that the species of Macrosporium are not as a rule 

 parasitic, and yet we have one British species destructive to Carnations, 

 and in Italy another species {Macrosporium Violce) is destructive to Violets. 



