HAWAII NATURE NOTES
THE PUBLICATION OF THE
NATURALIST DIVISION, HAWAII NATIONAL PARK
AND THE HAWAII NATURAL HISTORY ASSOCIATION

TREE FERNS

The five species of Hawaiian tree ferns recognized by botanists will appear quite similar to most visitors. The illustrations on the opposite page 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 on opposite page). 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.

Frond segments, segment closeups, and frond stalk sections of MEU (12) (left), HAPU III (9) (center), and HAPUU (11) tree ferns.