The Fungus Pests of Garden Plants 



THE LEAF DISEASE OF TOMATOES 



Dactylium roseuin, var. 

 (enlarged 300 diameters) 



on the Tomato plants but in the air, on the glass, and on the 

 shelves, pots, &c., which go to furnish a greenhouse. The name of 

 the fungus is Dactylium roseum, and it has been described as a 

 distinct species under the name of D. lycopersici. 



Another too familiar disease 



~ p. i of Tomatoes is popularly known 



\ / (\ Aj/^ as ' Black Spot.' This disease is 



also caused by a fungus, much 

 smaller in size than Dactylium 

 roseum, and named Cladosporium 

 lycopersici. The peculiar habit of 

 this fungus is first to attack the 

 pistil of the very young fruit ; 

 when once the minute pistil is 

 destroyed, as at A, the fungus 

 radiates from this point as a centre 

 and gradually invades the sub- 

 stance round the pistil in circles, 

 one circle beyond another, as seen in the illustration : the dead part 

 of the Tomato now becomes jet black and quite flat as shown. The 

 black stain is not confined to the exterior : it spreads deeply into 

 the interior, and turns the substance of the fruit into a putrid but 

 generally firm, and sometimes hard mass. As with the Dactylium of 



the leaves, the fungus spreads 

 from one plant to another with 

 great rapidity, but the growth 

 is never profuse with the 

 Cladosporium. Although the 

 fungus is sparingly produced, 

 it is certain and deadly in its 

 effects. When it is enlarged 

 three hundred diameters under 

 the microscope, it is seen as at 

 B. The habit resembles that 

 of the Dactylium, but the whole 

 growth, including the spores, 



is much smaller, and the spores themselves are pale brown, not 

 pink. 



Up to the present time both fungi have defied all attempts at 

 extirpation. They are both parasites ; their * roots ' or mycelia grow 

 within the plants attacked, and so are virtually beyond reach. 



426 



X-300 



THE 'BLACK-SPOT' DISEASE OF 

 TOMATOES 



Diseased fruit, natural size ; the parasitic fungus 

 Cladosporium lycopersici enlarged 300 diameters. 



