Typically recorded as "Eucalyptus," several genera have this
general morphology. Myrtaceae pollen is typically oblate and
triangular in polar view. The apertures are short furrows in a
thickened portion of the wall. The distinctive pattern typically
seen in polar view is formed by thinning of the exine,
resembling a syncolpium. This thin region often has a triangular
island of thick tectum at the pole of the grain. Sculpturing
varies from psilate to reticulate. Pollen of the Myrtaceae is an
important historic indicator in arid regions of the northern
hemisphere. Eucalyptus is the most commonly-planted genus, but
many other genera are used horticulturally. The morphology
similar to that described above also occurs in Acmena, Angophora
(retic.), Backhousia (no tectum island), Baeckea, Callistemon
(rough wall distinct island), Calytrix (broad aperatures),
Choricarpia, Leptospermum (faint tri-radiate mark), Lophostemon,
Melaleuca, Rhodamnia, Rhodomyrtus, Syzygium, Tristaniopsis, Ugni
About 3000 woody trees or shr