plasmodium

Plant body or vegetative growth of a slime mould, consisting of a large number of amoebae forming a mass with no firm wall. The plasmodium is microscopic in some species, but in others may weigh as much as 1 kg/2 lb. It lives on decaying organic matter often in soil, forming a fruiting body and producing minute spores that develop into new amoebae. Some are parasitic, for example Plasmodiophora brassicae, the cause of clubroot in brassicas.