Trigonospora

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Trigonospora

Distribution

Asia-Tropical:, Jawa (Jawa present) Burma: present Ceylon: present India except north-west: present Kwangtung: present Malaya northwards from 4°N: present N. Celebes: present N. Sumatra: present S. Sumatra: present
Ceylon, India except north-west, Burma to Kwangtung and southwards to Malesia; in Malesia: Malaya northwards from 4°N, N. Sumatra, S. Sumatra and Java, N. Celebes. About 8 species, not yet all described.

Cytology

Base chromosome number 36: T. ciliata diploid in Malaya; species of uncertain identity diploid and tetraploid in Ceylon and S. India.

Notes

This is the only group of species in the family in which trilete spores are normal, though such have been observed as occasional in Macrothelypteris (). In their shape and in their minutely papillose perispore they are closely similar to the spores of the monotypic African genus Menisorus Alston which are either spherical or monolete with a short laesura. Plants of Menisorus also have a short erect caudex and grow on rocks in streams; I believe that the two genera are related. An unnamed species in Ceylon has short capitate hairs, like those of Pseudocyclosorus, on the lower surface and on indusia.
In India and Ceylon this genus is much diversified in shape and size of fronds and of their pinnae, and in pubescence, but (apart from T. zeylanica Ching) individual species have not yet been clearly distinguished, probably because intermediates bridge some of the gaps between them. The existence of a tetraploid in S. India indicates hybridization; the habitat on wet rocks would facilitate this. One Ceylon specimen is very like T. calcarata of Java in shape of pinnae but much larger; others in Ceylon are very different. Hooker included most Indian specimens in Nephrodium calcaratum; Beddome added N. falcilobum Hook. (Pseudocyclosorus falcilobus Ching) as a variety, though it differs in its reduced basal pinnae. Hooker cited the type of T. zeylanica as a variety under N. falcilobum and expressed uncertainty as to a distinction between N. calcaratum and N. falcilobum.
Thelypteris khamptorum Holttum () has crenate pinnae and anastomosing veins, but agrees in spores with Trigonospora; two collections are known from Upper Burma.

Citation

Holttum - in Reinwardtia. 1974: 503