84 
ducing the disease. The vegetative filaments ramifying 
in the tissues of the leaf give rise to branches which pass 
out through the stomata and stand erect from the surface 
of the leaf. Food material is absorbed from the host 
plant by the vegetative filaments and is passed on to the 
reproductive branches. These produce large numbers of 
small two-celled spores, which being readily detached are 
disseminated by air currents. Under suitable conditions 
they germinate immediately on the surface of tomato 
leaves; each of the cells of the spore may send out 
a filament, which growing through one of the stomata, 
into the interior of the leaf produces a new infection. 
The careless watering of slightly diseased plants may 
carry spores to healthy leaves and thus spread the disease 
which is highly infectious. 
The disease only occurs in this country on tomatoes 
grown under glass, and though the spores described above 
are the only kind known, it is certain that they are able to 
survive the winter in the greenhouse and give rise to infec- 
tion the following season. If the houses are kept sufh- 
ciently well ventilated the disease seldom assumes serious 
importance; neglect of this precaution may, on the other 
hand, prove disastrous. It is possible to prevent any bad 
outbreak by regularly spraying with a Bordeaux mixture 
of half the usual strength, until the young fruit is begin- 
ning to set, when, owing to the poisonous character of 
Bordeaux mixture, Liver of Sulphur (1 oz. per 4 galls. of 
water) should be substituted. In order to prevent the 
disease recurring, all diseased leaves should be picked off 
immediately and dropped into a vessel containing a 
solution of copper sulphate; at the end of the season 
remains of plants should be burned and the greenhouse 
disinfected in the manner to be described in connection 
with the Cucumber-leaf disease. 
Several other diseases of the tomato plant, which are 
readily distinguished from the Leaf-rust described above, 
may be mentioned. The Sleepy disease caused by 
Fusarium lycopersici, is a wilt disease somewhat similar 
in symptoms to the Black-Leg of asters although caused 
by a very different fungus. |The Black-Stripe disease 
shows itself on the fruit and also sometimes on the stem 
as.a.dark, velvety growth of fungus. This disease, caused 
by Macrosporium solani, should not be confused with the 
Bacteriosis of the tomato in which blackening of the parts 
