Lignotubers: Australian plants have to survive extremely harsh conditions. Fire is common in many Australian environments. Native plants have developed a number of strategies to survive fairly frequent burning. Some species have woody fruits and cones to protect their seeds during fires (eg Banksias and Hakeas). Acacias have hard seed coats that require heat to break dormancy. Eucalypts and some members of the Proteaceae family have a swelling at the base of the stem at soil level or just below. This swelling is known as a lignotuber and contains dormant buds, which burst into life when the top growth is destroyed (usually by fire). These dormant buds produce suckers that develop into stems. Mallees are eucalypts with multiple stems produced from a lignotuber. The illustration shows the growth of a New England Mallee (E. codonocarpa). In this case the lignotuber is almost one metre (three feet) in diameter. The lignotuber and multiple stems have arisen due to the influence of bush fires. When this species grows in sheltered situations, protected from fire, or in cultivation then a single stem usually develops.