156 



INJURIOUS INSECTS AND FUNGI. 



[Sept. 1895. 



upper part of the figure, and the corresponding black dots on 

 the section of the tomato, it would appear that the fungus is 

 only able to penetrate the skin at the style, and before the 

 epidermis at that point has become completely closed. 



Dr. Plowright was the first to call attention to, and to name, the 

 fungus which causes this disorder. He described it in 1881 as 

 injuring tomatoes together with other fungi. But Dr. Plowright 

 considered the Claclosporium to be the conidium stage of a 

 Pkoma, and discovered another stage in the shape of the 

 macroconidia of Macrosporium lycopersici (M. tomato, Rav. ?). 

 These peculiarly-shaped macroconidia, with club-shaped ends, 

 as described by Dr. Plowright, were ; not noticed in tomatoes 

 recently examined ; it is, however, worthy of remark that the 

 disorder of tomatoes known in America as " black rot "• is 

 ascribed to Macrosporium tomato, Cooke, and the spores and 

 tufts of conidiospores as figured in the report of the section 

 of Vegetable Pathology of the United States Department of 

 Agriculture for 1888 exactly resemble those illustrating Dr. 

 Plowright's description of Macrosporium tomato. 



Another fungus has been noticed in tomatoes infected with 

 Cladosporium, lycopersici, having a somewhat dense mycelium 

 of threads more delicate and slender than those of the Clado- 

 sporium mycelium and quite colourless. This permeated the 

 tissues of the fruit and lived upon it, penetrating further into 

 the healthy tissues of the fruit than the Cladosporium, though 

 the Claclosporium was evidently the originator and main cause 

 of the mischief. It is by no means clear what is the species of 

 the other fungus, but it is probably a Fusarium similar in habit 

 to the Fusarium described in the American report alluded to 

 above, which was found with the Macrosporium tomato, and 

 said to be Fusarium solani. 



From the information that has been obtained with regard to 

 this disease it seems to be principally confined to tomatoes grown 

 in houses. It has been seen upon those produced out of doors, but 

 not nearly in such a serious degree, and this is because the spores 

 of the fungus are more readily communicated in the compara- 

 tively close quarters of a tomato house than in the open air. 

 The variations in temperature in tomato houses are also often 

 greater and more sudden than in the open air, unless the greatest 

 care is observed. In some cases, too, insufficient attention is 

 given to ventilation, and to the constant changing of the air — to 

 have, in short, a continuous circulation of air. In some span- 

 roof houses the sun shines on the glass fiercely in the day time, 

 and there is a great and rapid fall of temperature in the evening 

 and night. Too much moisture in the atmosphere of the 

 houses, especially when the temperature is very high, will also 

 cause an unhealthy condition predisposing the plants to fungoid 

 attacks ; watering and syringing should therefore be done 

 judiciously. 



