The five species of Hawaiian tree ferns recognized by botanists will
appear quite similar to most visitors. The illustrations below show
several of the differences. Most common of the tree ferns are the two
species called HAPUU (10, 11) which do not have the coarse bristles of
the HAPU III (9) which sometimes grow to a height of 35 feet, including
the fronds. The fourth species, the MEU (12), is not common, and is
found only on the island of Hawaii. A fifth species is frequent in the
highlands of Kauai.
The reproductive bodies of the tree ferns are borne in small, bead-like
capsules on the margins of the leaf segments (see illustration below).
These capsules, which open by means of small lids, may be responsible
for the generic name of the ferns, _Cibotium_, from a Greek word meaning
a small vessel.
The buds of these ferns are covered with the silky PULU, discussed
below. According to Hillebrand (5, p. 546) ferns of the genus _Cibotium_
range over Mexico and Central America, the Philippine Islands, Sumatra,
South China and India. It is an interesting speculation as to which of
these places provided the spores which gave the Hawaiian tree ferns
their beginning.
Much of what appears to be the trunk on these and many other ferns is in
reality a useful mass of aerial roots which absorb moisture and protect
the tree trunk from damage. These roots also offer a fertile place for
seeds of many other plants to take root and grow. So common is it to
find ohia trees growing on tree fern trunks that the ferns are often
called _mother of ohia_. Unappreciative of the support given them in
their early growth the trees often send roots to earth which become so
large that the fern finally is killed. Much starch is present in the
trunks of tree ferns. This was resorted to by the Hawaiians for food in
time of famine. Young fronds of the tree ferns are used in preparing
several exotic dishes today, and many Park ferns have suffered severely
by having the new growth removed for this purpose.
[Illustration: Multi-branched fronds characterize tree-ferns]
[Illustration: Frond segments, segment closeups, and frond stalk
sections of MEU (12) (left), HAPU III (9) (center), and HAPUU (11)
tree ferns.]