108 DISEASES OF GLASSHOUSE PLANTS 
beneath the epidermis of the leaf, and with age the 
epidermis bursts and breaks away leaving a mass of tiny 
rust-brown spores (Figs. 28, 29). Thus typically infected 
leaves are densely spotted with tiny rusty pustules, the 
majority of which are formed on the underside of the 
leaf. At one time it was thought that the rust of 
chrysanthemums was the same as that which attacks a 
large number of plants of the same family, but Arthur 
has shown that it is not so, and that the chrysanthemum 
rust will not attack any other plant. This disease is 
caused by Puccinia chrysanthemi Roze. 
It is carried from season to season by means of 
cuttings and old stock plants, and it is important that 
cuttings should be made solely from healthy stock. 
Dusting with sulphur powders is generally practised as a 
means of keeping the disease in check. Under glass it is 
rarely serious, and in fact need not be feared by careful 
growers, as attention to ventilation, careful watering, and 
selection of stock is sufficient to effect a control. The 
disease is frequently imported on new stock, which should 
be carefully examined for signs of it. Miss Clay Frick 
(white), Niveus (white), W. Duckham (pink), and W. H. 
Lincoln (yellow) have proved to be highly susceptible to 
rust. Cheshunt White, Heston White, Ivy Gay (mauve- 
pink), Kathleen May (red), Mrs. Henneage (yellow), 
Nagoya (yellow), Mlle. R. Pancouche (white), Romance 
(yellow), and Winter Cheer (pink) are moderately suscep- 
tible. Baldock’s Crimson, Gladys Lane (bronze), Hortus 
Tolosanus (bronze), Mme. R. Oberthur (white), Tuxedo 
(bronze), The Favourite (white), and Winter Gem (yellow- 
bronze) have proved highly resistant. 
Chrysanthemum Leaf Blight.—This disease, caused by 
Cylindrosporium chrysanthemi K. and D., makes rapid 
progress once a plant is attacked. It is not common in 
this country, but when it occurs serious damage results. 
Large dark brown patches are formed on the leaves. 
The tissues round the patches turn yellow and the leaves 
