Tectaria

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Tectaria

Distribution

Pantropic: present
Pantropic; c. 210 species, of which c. 40 are neotropic.

Taxonomy

In describing the new genus Tectaria, Cavanilles cited only one species which is therefore the type, but he later included in the same genus other species which are now placed in Dryopteris, Polystichum, Nephrolepis, Thelypteris and other genera, their common character being sori covered with reniform or peltate indusia. In 1801 Swartz established the genus Aspidium with a similar wide-ranging content, including the original species cited by Cavanilles.

Later authors adopted Swartz's name and treated it variously. Presl, Fée and others attempted to segregate genera on the basis of characters of indusia (whether peltate or reniform) and of venation; they are listed by Christensen (1905). But these 19th century authors did not observe indusia critically and failed to notice other characters now seen to be important, especially of hairs, scales and glands, and most of their generic names are no longer recognized, or if recognized are defined mainly by characters not mentioned by their original authors. Hooker (1862) and Baker (1867), attempting to establish genera of wider scope, confused together unrelated species. It was not until the classification of Diels (1899) that it was clearly recognized that species belonging to the same genus could have, or lack, indusia; he transferred some exindusiate species to Aspidium. But Diels included also some extraneous elements and his subdivision of Aspidium is valueless. Christensen (1905) cited many generic synonyms but his main subdivision of Aspidium is little better than that of Diels; he did however recognize that, of the synonyms cited, Tectaria has priority and printed against it 'nom. opt. '. Soon afterwards Copeland (1907), actively studying Philippine species, revived the name Tectaria for them, but Van Alderwerelt (1908) attempted to revert to the form of indusia to characterize infrageneric groups, misusing the name Sagenia Presl. Christensen accepted the generic name Tectaria in the third Supplement to his Index (1934), Ching having already (1931) made the first good study of the species of mainland Asia.

Ching and Copeland accepted in Tectaria only species with anastomosing veins. Copeland (1907: 409) however wrote 'Dryopteris dissecta (Forst.) Kuntze represents, most nearly of known species, the probable origin of Tectaria. ' But at that time Christensen had not yet discovered a natural subdivision of the comprehensive Dryopteris of his Index. When he did so (in his monograph of 1913 and 1920), working entirely with tropical American species, he distinguished Ctenitis from Dryopteris s. str. (and from thelypteroid ferns) by the character of its hairs, and pointed out that in its hairs Tectaria agrees with Ctenitis. Ching dealt with the species of Dryopteris and Ctenitis of mainland Asia in 1938 and in so doing came across a few species which have free veins but in other respects resemble Tectaria. He proposed a new genus Ctenitopsis for these species (one was Forster's dissecta) and also species with free veins later transferred by Holttum to Hetero- gonium; Copeland (1947) transferred all these to Ctenitis and wrote (p. 124) 'Tectaria is probably of ctenitid origin' and (p. 130) 'Ctenitis is more primitive than Tectaria, therefore it is the probable parent genus.' By the latter comment he meant that anastomosing veins are a specialized character as compared with free veins and that therefore the primitive species of Tectaria had free veins. But Copeland overlooked the fact that the type species of Ctenitis, and most other American species included in that genus by Christensen, differ from Tectaria in their scales and also in bearing cylindric glands which are lacking in Tectaria-, Manton (1954) also showed that they differ in chromosome number. Forster's species which was the subject of Copeland's comment in 1907 differs only from acknowledged species of Tectaria in its free veins, and the species T. fuscipes (Bedd.) C. Chr. bridges the gap by having veins anastomosing to form costal areoles in its sterile fronds but all free in fertile ones. The free-veined species here accepted in Tectaria are most abundant in mainland Asia (NE India and China) and in the Philippines. There are a few others in Malesia and the Pacific but no related species in tropical America or in Africa . Thus SE Asia is here regarded as the centre of origin of the genus. Tectaria ingens (Atk.) Holttum in NE India has fronds up to 3 m tall (including the stipe) and is perhaps the nearest existing species to a prototype for the genus.

In considering a subdivision of Tectaria, vein-pattern appears to be our only guide, and the clearest division is between species which have veins free or anastomosing in the pattern indicated for Sagenia by Presl, and those which have copious anastomosis with branched veinlets in the areoles as in the type species of Tectaria. There are, however, in Peninsular Thailand and Peninsular Malaysia, especially on limestone, intermediates between the two. Apart from these species, a distinct line can be drawn between species which have narrow costal areoles lacking included free veinlets and those in which costal areoles do contain free veinlets. The division is here accepted, with sectional rank for the two divisions. As sect. Sagenia is clearly the primitive group, it is dealt with first.

Cytology

Chromosome number 40.

Citation

Copl., Gen. Fil. 1947: 128
Backer & Posth., Varenfl. Java. 1939
M. G. Price - in Kalikasan. 1974: 175
J. Sm., Hist. Fil. 1875
Sledge - in Kew Bull. 1972: 422
Alderw., Malayan Ferns. 1908
Ching - in Sinensia. 1931
Copl. - in Philipp. J. Sci. 1928: 402
Holttum - in Revis. Fl. Malaya. 1955
Manton & Sledge - in Philos. Trans. Sér. B. 1954: 137, 160
C. Chr., Index Filic. 1905: xxii
Copl., Fern Fl. Philipp. 1960
Copl., Fern Fl. Philipp. 1960: 317
Copl. - in Philipp. J. Sci. 1907: Bot. 409-418
Holttum - in Gard. Bull. Sing. 1986: 154
Diels - in E. & P., Nat. Pflanzenfam. I. 1899