Light micrograph of the root of a cabbage infected with the parasitic slime mould Plasmodiophora brassicae, the cause of club root. The fungus attacks cruciferous plants such as wallflowers, stocks, turnips and radishes and is especially damaging to brassicas (cabbages, cauliflowers, sprouts etc. ). Infection occurs through the young root hairs, and the fungus spreads into the cortical cells below the epidermis. Here it stimulates cell division, resulting in the characteristic clubbing of the roots. As the roots decay, resting spores are released into the soil, where they can remain viable for many years. Magnification: x50 at 35mm size.