Gleicheniaceae

Primary tabs

Gleicheniaceae

Distribution

New Caledonia: present Throughout the wetter parts of the tropics and subtropics: present in the tropics mainly on mountains, at lower altitudes in southern temperate regions: present mainly tropical, atlow and moderate altitudes: present south temperate regions: present
Throughout the wetter parts of the tropics and subtropics, and in south temperate regions. Three genera: Stromatopteris (monotypic, in New Caledonia), Gleichenia (3 subgenera, c. 150 species, in the tropics mainly on mountains, at lower altitudes in southern temperate regions), and Dicranopteris (2 subgenera, c. 10 species, mainly tropical, atlow and moderate altitudes). Dicranopteris is much more polymorphic in Malaysia than in any other part of the tropics. (The genus Platyzoma is excluded from the family; see ).

Anatomy

The rhizome has a simple protostelic structure except in Dicranopteris pectinata (see Bower, l.c.). The rachis has a single C-shaped vascular Strand; all the outer tissues in the rachis are thick-walled and when mature form a very strong protection for the vascular Strand. Such protection is important in fronds which continue to grow in length for a long period.

Taxonomy

I published a Statement on taxonomy, with discussion of the present arrangement, in 1957 (). Copeland () divided the Malaysian members into four genera. It seems to me, however, that Dicranopteris is so different from the rest that a main division should indicate this difference, and I therefore recognize two genera, Gleichenia and Dicranopteris, the former with three subgenera which correspond to Copeland's genera. For one of the latter he used the name Hicriopteris Presl, but the type species of that genus is a Dicranopteris (described as D. speciosa in the present work). I have therefore adopted the subgeneric name Diplopterygium, first proposed (as a sectional name) for this group of ferns by Diels (). For the other subgenus the name Mertensia is available; it was first used in this rank by Hooker, though with a larger content. This name was first proposed by Willdenow in 1804 as a generic name to cover all known members of the family with larger divisions of the lamina than the original G. polypodioides (Thunb.) Smith; but as a generic name it was antedated by Mertensia Roth (Boraginaceae) and so it is illegitimate. In 1806 Bernhardi published the generic name Dicranopteris, citing under it only one species of Mertensia Willd., viz Polypodium dichotomum Thunb., which thus becomes the type species of Dicranopteris. I have typified Mertensia by the species M. truncata Willd. (). Both Mertensia and Dicranopteris are used here in a more restricted sense than intended by some earlier authors. Copeland used the generic name Sticherus Presl for subg. Mertensia of the present account. This name was established by Presl for two species of which he had seen no specimens, with a brief and confused description, and the lapse of the name is not to be regretted.

Cytology

Manton & Sledge () report for Dicranopteris linearis from Ceylon both n = 39 and n = 78; from Singapore, for what is now recognized as D. cur- ranii Copel., n = 39. Manton reports verbally that a plant of D. linearis sent from Singapore and cul- tivated at Kew is a sterile triploid hybrid. Mehra & Singh also report n = 39 for D. linearis from Northern India (), and n = 56 for Hicriopteris glauca (probably Gleichenia gigantea Wall., which is the common Himalayan species of this group), a species of Gleichenia subg. Diplopterygium. Brownlie () reports n = 20 for G. (subg. Gleichenia) microphylla R. Br. and n = 34 for G. (subg. Mertensia) cunninghamii. T. G. Walker reports (personal communication) n = 34 for two species of subg. Mertensia from Jamaica. The structure of sporangia has been fully described by Bower (). Both trilete and monolete spores occur in the family. Nakai (l.c.) proposed a basic division of the family on spore-form, but in so doing he supposed that only trilete spores occur in his restricted genus Dicranopteris (D. linearis and its near allies); in fact closely related species of this group have spores of different forms, and a division of the family on spore-form is certainly unnatural. The most recent and most complete account of gametophytes in the family is by A. G. Stokey () and includes references to earlier accounts. Species of all genera and subgenera here recognized were studied. Dr Stokey's conclusion is that the gametophyte in all cases shows many primitive characters, but there is little significant difference within the family to indicate that one part is more primitive than the rest. Gleichenia subg. Gleichenia shows specialized characters (notably the long neck of the archegonium) and on characters of the gametophyte is judged to be further removed from the rest of the family than they are from each other. Two-celled hairs of a peculiar nature have an origin similar to that of the larger hairs on prothalli of Cyatheaceae; apart from these hairs, the prothalli of Gleicheniaceae most resemble those of Dipteris.

Uses

Heyne () records the following uses for parts of plants of this family; the chief species used are Dicranopteris linearis and D. curranii. The rachises of mature fronds are tied into bundles and the bundles used in making the fences of a certain kind of fish trap; they will last two years when immersed in sea-water. Parts of the rachis of a large frond (the largest are produced by D. curranii) when suitably split make excellent pens for writing Arabic characters (I learned of this use also in Singapore). The vascular strands of stipe and rachis are separated and used for special kinds of fine plaited work, being strong and pliable.

Dicranopteris thickets may be useful as preventing erosion, but they are troublesome to the forester when they prevent regeneration of tree-seedlings in forest Clearings. As the rhizomes are almost or quite superficial, they are exposed when the thicket is cut down, and usually one such cutting is enough to kill almost all of the plants. Fronds are sometimes cut — when in absence of other suitable material —• to provide light shade for transplanted seedlings.