Dicranopteris
Content
Distribution
Malaysia present, equatorial lowlands present, wetter parts of the tropics and subtropics present
Thicket-forming ferns, abundant in open places throughout the wetter parts of the tropics and subtropics, especially characteristic of equatorial lowlands (the species of Gleichenia being almost exclusively mountain plants in Malaysia).
Cytology
Haploid chromosome number of D. curranii Copel. (Singapore) is 39. D. linearis (apparently the normal form of the species) in Ceylon is either diploid (n = 39) or tetraploid (n = 78); a plant of D. linearis sent to Kew from Singapore is a sterile triploid.
Notes
There are two well-marked subgenera, Dicranopteris (pantropic) and Acropterygium (one species, in tropical America; no accessory branches, rhizome with solenostele).
The subgenus Dicranopteris is much more diversified in Malaysia than in any other part of the world. A small group of species may be clearly distinguished by their monolete spores. Almost all other specimens are at present regarded as belonging to a polymorphic species, D. linearis. Some of the varieties of D. linearis are more clearly distinct than others, and probably should be recognized as species. They need, however, to be more clearly characterized from field studies. The existence of a triploid hybrid (see note below on cytology) indicates that it is probably impossible to refer every plant to a clearly defined variety.
Four varieties of D. linearis have the common character of invariably producing accessory branches at the bases of ultimate branches; in other characters they differ considerably from each other and do not form a natural group. Another variety having this character occurs commonly in west tropical Africa, but no such variety has been found in east Africa.
The subgenus Dicranopteris is much more diversified in Malaysia than in any other part of the world. A small group of species may be clearly distinguished by their monolete spores. Almost all other specimens are at present regarded as belonging to a polymorphic species, D. linearis. Some of the varieties of D. linearis are more clearly distinct than others, and probably should be recognized as species. They need, however, to be more clearly characterized from field studies. The existence of a triploid hybrid (see note below on cytology) indicates that it is probably impossible to refer every plant to a clearly defined variety.
Four varieties of D. linearis have the common character of invariably producing accessory branches at the bases of ultimate branches; in other characters they differ considerably from each other and do not form a natural group. Another variety having this character occurs commonly in west tropical Africa, but no such variety has been found in east Africa.