ERYSIPHALES

an important family of ascomycetous Fungi, distinguished by the presence of typical sexual organs and closed ascus-fruits (cleistocarps) which bear characteristic appendages concerned with dispersal; also by the fact that each segment of the septate mycelium contains a single nucleus. They are all parasites, appearing on leaves, stems, or fruits as white patches of mycelium (‘mildew’). During summer innumerable conidia are produced, which spread the disease rapidly; in autumn the black ascus fruits develop and carry the fungus through the winter. Erysiphales are responsible for many important plant diseases, e.g. the mildew of hops (Spherotheca Castagnei), vine (Uncinula spiral is), wheat (Hrysiphe communis), and the American gooseberry mildew (Spherotheca Mors-uve), a *‘notifiable” disease in Britain.