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 fiJaments 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 suffi- 

 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 'i oz. per 4 galls, of 

 water) should be substituted. In order to prevent the 

 disease recurring, all diseased leaves should be picked oft^ 

 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 

 wdth the Cucumber-leaf disease. 



Several other diseases of the tomato plan t,_^ which are 

 readily distinguished from the Leaf-rust described above, 

 m^ay be mentioned. The Sleepy disease caused by 

 Fii'sarimii lycopersici. is a v\-ilt disease somewhat similar 

 in symptoms to the Black-Leg of asters although caused 

 by a very different fungus. llie 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 Macros poriitm solam, should not be confused with the 

 Bacteriosis of the tomato in which blackening of the parts 



