Marattiaceae

Description

The Marattiaceae diverged from other ferns very early in their evolutionary history and are quite different from many plants familiar to people in temperate zones. Many of them have massive, fleshy rootstocks and the largest known fronds of any fern. The Marattiaceae is one of two groups of ferns traditionally known as eusporangiate ferns, meaning that the sporangium is formed from a group of cells as opposed to a leptosporangium in which there is a single initial cell. At least two genera, Angiopteris and Marattia, have been reported to undergo monoplastidic meiosis rather than polyplastidic meiosis, and are the only known examples within euphyllophytes to do so.

The large fronds characteristic of the group are most readily found in the genus Angiopteris, native to Australasia, Madagascar and Oceania. These fronds may be up to 9 meters long in the species Angiopteris teysmanniana of Java. In the Hawaiian Islands, Costa Rica, and Jamaica, the species Angiopteris evecta is naturalized, having escaped from botanical gardens, and is considered an invasive species. Angiopteris is unique among ferns in having explosively dispersed spores, which may contribute to its ability to spread.

Marattia in the strict sense is found in the neotropics and Hawaii with six recognized species. The genus Eupodium is also neotropical, with three species, and was originally described for the distinctive stalked synangia of some species.

Ptisana is a paleotropical genus, formerly thought to be part of Marattia. These plants are 2-4 times pinnate, with fronds often comparable in size to those found in Angiopteris. Terminal segments usually have a prominent suture where they attach. The sporangia lack the labiate apertures of Marattia and Eupodium, and synangia are deeply cut. The name of the genus derives from the resemblance of the synangia to pearl barley. The king fern, Ptisana salicina, from New Zealand and the South Pacific and known in Māori as "para" now has been placed in this genus. Sometimes called the potato fern, this is a large fern with an edible fleshy rhizome that is used as a food source by some indigenous peoples.

The East-Asian genus Christensenia, named after the Danish pteridologist Carl Christensen, is an uncommon fern with distinctive fronds resembling a horse chestnut leaf, hence the species Christensenia aesculifolia, meaning horse-chestnut-leaved Christensenia. Despite the relatively diminutive size of plants in this genus, the stomata of Christensenia are the largest known in the plant kingdom.

The genus Danaea is endemic to the Neotropics. They have bipinnate leaves with opposite pinnae, which are dimorphic, the fertile leaves much contracted, and covered below with sunken, linear synangia dehiscing via pores.