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Description

Hairs consisting of several cells, not intergrading with scales, variously present on most parts of the frond, the prominent upper surface of costae of lamina-segments in a majority of cases (at least near the base) covered with short erect hairs of several cells, the outer cell-walls thin and collapsing on drying (in other cases hairs in this position may remain firm on drying);

Distribution

Old World: present Pantropic: present
Pantropic with greatest diversity in the Old World; about 20 genera.

Taxonomy

In the 19th century the form of sori and condition of venation (free or anastomosing) were by most authors regarded as the most important bases for classification. Thus the free-veined members of the present group were associated with Dryopteris and free-veined Thelypteridaceae, and exindusiate species were separated generically. This led to confusions of various kinds.

The first major work in the 20th century was Christensen's subdivision of the unnatural aggregate of species under Dryopteris in his Index Filicum (1905) which included all free-veined ferns with reniform indusiate sori and their obvious exindusiate relatives. For the first time he distinguished Ctenitis from Dryopteris, pointing out the relationship of the former to Tectaria and also the distinctive characters of thelypteroid ferns (some of which have anastomosing veins). In his last major survey of the classification of all ferns (1938) he retained a major family Polypodiaceae with Dryopteridoideae as one subfamily; this included, in section A, Dryopteris and Tectaria with other genera related to them, with Thelypteridaceae in section B.

In 1940 Ching divided Christensen's Polypodiaceae into several families, one being Aspidiaceae, similar to Christensen's Dryopteridoideae section A of 1938. Ching divided it into two tribes, Aspidieae and Dry opter ideae. In 1947 Holttum accepted Ching's two tribes, with minor changes, but placed them as subfamilies in a major family Dennstaedtiaceae, with the idea that Polypodium and its immediate allies form a very different group of ferns. Copeland, writing independently in 1947, recognized a large family Aspidiaceae, including Thelypteris and its allies, also Athyrium/Diplazium and the Lomariopsis group of genera. In his conspectus (1947: 153) the genera here dealt with appear as allies of Ctenitis; to them should be added Cyclopeltis which he associated with Polystichum, and Dryopolystichum excluded. Pichi Sermolli (1977) included both dryopteroid and tectarioid genera in his family Aspidiaceae and did not accept a division of it into two groups.

Holttum (1984) discussed the above history in more detail, still retaining separate groups associated with Dryopteris and Tectaria and objecting to the Tryons' arrangement in their book of 1982 in which the two groups are confused. In 1986 Holttum presented a conspectus of all Old World genera of the Tectaria alliance, with comments on those of the New World, pointing out the peculiar characters of Dryopsis Holttum & Edwards which perhaps connects the two groups. Most species of Dryopsis are in Mainland Asia but two are Malesian.

The structure of the junction of the bases of leaflets and the rachis that bears them is here presented as the most clear distinction between the genera allied to Dryopteris and those allied to Tectaria. This is seen best in Lastreopsis, Ctenitis and Pteridrys (see fig. 311 in Holttum 1955: 524). In Lastreopsis the relationship is exactly as in Davallia; Ctenitis only differs in the margins of the lamina which are not thickened where they are decurrent on the rachis-wing. In Cyclopeltis the relationship of pinna-base to rachis is only evident near the apex of the frond. An arrangement close to Davallia is also shown by Rumohra, a genus included by several authors in Aspidiaceae. But Rumohra differs from all the genera here included in its strongly dorsiventral rhizome-structure, comparable to that of Davallia though not identical with it, and also in its scales. Rumohra differs from Davallia in its distribution (widely in South America, also in southern Africa and Australasia) and in its spores. In Malesia, it only occurs in New Guinea. It is perhaps a connecting link between Davallia and the Tectaria group; it needs a comprehensive new morphological study.

Pichi Sermolli (I. c. 1977: 238) has stated that there are four different types of rachis-structure in Aspidiaceae but he deals only with the junctions of main rachis with pinna-rachises, not with the relationship between lamina- elements and the smaller distal rachises which I believe to be significant. I have expressed disagreement with him in 1984 (l. c.: 314).

Cytology

Base chromosome number 40 or 41.

Citation

in Revis. Fl. Malaya. 1955: 494
Studies fern genera I in Fern Gaz. 1984
Studies fern genera VI in Gard. Bull. Sing. 1986