Sentence:  &#91;[https://books.google.com/books?id=4UsHOAGc5x0C&dq=mallees&pg=SA1-PA4 page 1-4, section 1.3]&#93; Of the many variations in form of the <u>Eucalyptus</u> (shrubs, <WSD>mallees</WSD>, trees, etc.), virtually all species being tested in the above category are those which exhibit good tree form (e.g., height, straightness of trunk, etc.). / &#91;[https://books.google.com/books?id=4UsHOAGc5x0C&dq=mallees&pg=SA2-PA1 page 2-1, section 2.2]&#93; Shrubby eucalypts are usually referred to as "<WSD>mallees</WSD>" although the term strictly applies to those species which have many stems growing from an enlarged rootstock (lignotuber). 
Meaning of the word marked with <WSD> tags:  The growth habit of certain eucalypt species that grow with multiple stems springing from an underground lignotuber, shared by species of related genera.