268 VEGETABLE FOES AND DISEASES 



through minute cracks in the cuticle or skin. This 

 is emphasised by the fact that the fruit is usually 

 affected round the style, or at the point of insertion of 

 the stem, where minute cracks frequently occur. The 

 fungus, however, appears on any part of the fruit, and 

 also on any portion of the stem and leaves. It appears 

 that the chief seats of disease are where moisture has 

 rested in the parts some time, and the germ-tube of a 

 spore of the fungus being present, may either have 

 entered by a minute crack in the cuticular cells or 

 directly pierced through the softened cuticle. 



The affected part has, at first, a white blister-like 

 appearance, as if due to scorching or scalding, and is a 

 little below the general surface of the healthy part of 

 the stem, leaves or fruit. As the dark-coloured my- 

 celium of the fungus forms in the tissues, the diseased 

 spot assumes a dark or black colour, for the parasite 

 rapidly destroys the cells, and consequently the affected 

 part sinks, forming a depressed blotch, spot or stripe. 

 Later, the sunken surface becomes covered with a deli- 

 cate velvety pile, in places, of a brownish or blackish- 

 olive colour. This outgrowth is, under microscopic 

 examination, found to consist of closely packed, dark- 

 coloured conidiophores, each bearing a dark, many- 

 celled conidium at its tip. The conidia, when mature, 

 germinate quickly in water, each cell or spore producing 

 a germ-tube capable of infecting a Tomato if placed 

 on a surface susceptible to entrance. 



Prevention. All diseased parts should be cleared 

 away and burned, otherwise the " fruits " of the fungus 



