For this reason Fungi are perhaps best described as plant like micro-organisms that do not possess chlorophyll. Typical moulds on the other hand, are more complex, multicellular fungi, of variable appearance and colour. It is this mycelium that is largely responsible for the formation of exzymes, fungal toxins, etc.
Many fungi also have a sexual stage in their life cycle.
Whereas fungi that attack growing plants are fairly restricted in number and are true pathogens, fungi in stored products are much more numerous and are saprophytic, or only weakly pathogenic by nature. This also applies to the 'field fungi'. The Fusarium group is also important at this stage. Once in store the field fungi tend to decline, their place being taken by such typical storage groups as Aspergillus and Penicillium. By-products of the normal growth process are often of a complex chemical nature and may be beneficial but are sometimes undesirable.