Cyatheaceae

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Cyatheaceae

Distribution

America: present Australasia: present present Azores: present Juan Fernandez: present Malaysia: present present present present present Pacific:, Hawaii present SE. Asia: present Southern America: St Helena: present a few species just north of the tropics, more south of the tropics especially in Australasia: present tropical America: present present present tropical S. America: present wetter parts of the tropics, especially on mountains: present
Throughout the wetter parts of the tropics, especially on mountains; a few species just north of the tropics, more south of the tropics especially in Australasia. As here construed, 9 genera, of which 5 are Malaysian: Cyathea (pantropic, at least 600 spp.); Cnemidaria (limited to species with simply pinnate fronds, anastomosing veins and distinctive spores, tropical America, 10 spp.); Lophosoria (tropical America, monotypic); Dicksonia (tropics and southern subtropics in Malaysia, Australasia, America, St Helena, c. 25 spp.); Cystodium (Malaysia, monotypic); Thyrsopteris (Juan Fernandez, monotypic); Culcita (subg. Culcita in Azores and tropical America; subg. Calochlaena in Malaysia and Australasia; in all c. 7 spp.); Cibotium (SE. Asia, Malaysia, Hawaii, Central America, c. 12 spp.); Metaxya (tropical S. America, monotypic).

Anatomy

The first critical account of anatomy in this family was by Mettenius, in the course of his study of Angiopteris (.) The most recent full account of the anatomy of members of Cyatheaceae is by Ogura ().

U. Sen has recently completed a new anatomical study of the family, summarized in Holttum & Sen (). The vascular structure, with its accompanying sclerotic tissue, is very similar in all Malaysian genera except Cibotium; it is most fully developed in Cyathea, to which the following notes apply. As seen in a transverse section of the trunk, there are several meristeles, with gaps between them, together forming a hollow cylinder, the gaps corresponding to leaf-bases. On the outer and inner sides of each meristele are plates of very hard sclerotic tissue. Small vascular strands arise from the margins of the gaps and supply the leaves, and in Cyathea there are also small medullary bundles which anastomose with each other and with the meristeles. Distinctive 'cubical cells' form a more or less continuous layer surrounding each mass of sclerenchyma; their walls adjacent to each other and to the sclerenchyma are much thickened, and they contain crystals which appear to be silica. The sclerotic tissue, with its cubical cells, is lacking in Cibotium. In the phloem are tangentially elongated cells, in structure like the longitudinal sieve-tubes; such cells are only otherwise known to occur in Osmunda. The pattern of arrangement of the numerous vascular strands in the stipe of Cyathea is distinctive; in other genera they are more or less joined. In the smaller axes of the frond the pattern is progres- sively simplified. The stomata of Cibotium show more complex developmental stages than those of the other genera.

Economic importance. Ochse & Bakhuizen van den Brink reported the use of coiled young fronds of Cyathea contaminans and C. junghuhniana (mis-named C. latebrosa) as food, also the pith of young parts of the trunk of the former species (). Other species (perhaps all) are similarly edible; Hoogland notes this of some from the mountains of New Guinea. The pith of trunks was formerly eaten by Maoris in New Zealand. The common name in Java and Sumatra for the larger tree-ferns, Pakis (or Paku) tiang (tiyang, teehang), indicates the use of the trunks as posts; this name does not seem to have been noted in the Malay Peninsula. The sclerenchyma of most tree-fern trunks is exceedingly hard and durable, and provides nearly all the mechanical strength when they are used as posts. It also provides an interesting pattern when cut in different ways, and this effect is used in the construction of ornamental objects in various parts of the world. In North Borneo I noted old tree-fern trunks, hollowed out, in use as bee-hives around Dusun houses. On Mt Patuha, W. Java, hollowed tree- fern trunks are filled with carbide gas for making booms on New Year's eve. The masses of adventitious roots at the bases of Cyathea trunks are used in orchid culture, either as solid slabs (cut with a saw) or broken, in potting mixtures.

Taxonomy

Bernhardi (in ) attempted a Classification of ferns according to the form and position of the annulus of a sporangium, proposing a division into Helicogyratae (including Cyathea and Dicksonia), Cathetogyratae (majority of leptosporangiate ferns), Pseudogyratae (including Gleichenia) and Agyratae. Presl () varied this by associating Gleichenia and Cyathea (sens. lat.)in Helicogyratae and placing Dicksonia (under the namq Balantium) in Cathetogyratae. Hooker () arranged all ferns in seven suborders, all genera here treated being included in suborder Polypodiaceae; they are divided astribe Cyatheae (Cyathea, s.l.) and tribe Dicksoniae (all other genera, also some additional ones). Mettenius () arranged all ferns in eight orders, of which the second was Cyatheaceae, which corresponded exactly with the present arrangement with the addition of Matonia (Mettenius used the name Balantium in place of Dicksonia), Christ (), Diels (in ) and Christensen () adopted a family Cyatheaceae with the same content as the order Cyatheaceae of Mettenius, with omission of Matonia. Bower, however, believed that Cyathea and its near allies should be associated closely with Gleicheniaceae, as one of the more primitive elements of the series Superficiales, while he placed Dicksonia and allies in the series Marginales, regarding the Separation of the two as 'long overdue' (). This idea was followed by Christensen in 1938 (in ), where he recognized two families, Dicksoniaceae and Cyatheaceae. Bower's arrangement involves the assumption that primitive Cyathea, like Gleichenia, was exindusiate, so that indusia in his Cyatheaceae are a new development, not homologous with the inner indusium of Dicksonia (l.c. 304). In this he disagreed with Goebel (), who regarded the indusium of Hemitelia (now included in Cyathea) as strictly homologous with the inner indusium of Dicksonia. Copeland (Gen. Fil., 1947) included Dicksonia and allies in a family Pteridaceae, associating with them Lindsaea, Dennstaedtia, etc., while maintaining Cyathea s.l. in a separate family Cyatheaceae. Holttum & Sen have published a discussion of the whole question (), with the conclusion that Goebel's contention was correct; they give a new subdivision of the family Cyatheaceae, as here constituted, based partly on new evidence. This subdivision is sum- marized as follows.
Conspectus of the familySubfamily Cyatheoideae. Fronds normally bipinnate with lower pinnae more or less reduced; pinnules almost symmetrical; upper surfaces of costae and pinna-rachis raised (or, if grooved, the groove of a major axis not open to admit that of a minor one borne upon it); sori terminal on veins or on lower surface of veins, indusiate or not; dermal appendages hairs or scales or both; cubical cells present in association with sclerenchyma; stomata with single subsidiary cell.2Subfamily Thyrsopteridoideae. Fronds 3-4-pinnate, lowest pinnae largest; leaflets asymmetric; upper surface of axes and of leaflet- midribs grooved, grooves of major axes open to admit those of minor ones; sori at ends of veins; cubical cells present; stomata with single subsidiary cell.5Subfamily Cibotioideae. Fronds normally bipinnate; pinnules almost symmetrical; upper surfaces of pinna-rachises and costae raised; sori terminal on veins, shape much as in Dicksonia but with outer and inner indusia both unlike the lamina of the frond, lacking Chlorophyll and lacking intercellular spaces; sclerenchyma and cubical cells lacking; stomata with 3 subsidiary cellsCibotiumSubfamily Metaxyoideae. Fronds simply pinnate, pinnae lobed on young plants only; upper surface of rachis and of midribs of pinnae grooved, groove of rachis open to admit grooves of pinna-midribs; sori superficial on lower surface of veins, usually more than one to a vein, no indusium; sclerenchyma and cubical cells lacking; stomata with 3 subsidiary cells (1 sp., tropical America)MetaxyaTribe Cyatheae. Scales and hairs present as dermal appendages; sori superficial, indusiate or not; cubical cells in continuous layer on surfaces of sclerenchyma.3Tribe Lophosorieae. Hairs only as dermal appendages; sori superficial, no indusia; cubical cells singly in association with sclerenchyma (1 sp., tropical America)LophosoriaTribe Dicksonieae. Hairs only as dermal appendages; sori marginal, protected by slightly modified marginal lobe of lamina (outer indusium) and a thinner inner indusium; receptacle of sorus fused to inner indusium.4Fronds mostly bipinnate; veins almost always free; spores with thin walls of uniform thickness, smooth or papillose; indusium various or lackingCyatheaFronds simply pinnate with anastomosing veins; spores with wall much thickened, a spherical hollow in the middle of each face; indusium hemitelioid (c. 10 spp., tropical America)CnemidariaFronds bipinnate with deeply lobed pinnules, or tripinnate; stem usually a thick erect trunk; cubical cells as in CyatheaeDicksoniaFronds bipinnate with simple pinnules; stem prostrate; condition of cubical cells not known.CystodiumTribe Thyrsopterideae. Fertile and sterile parts of frond strongly dimophous (lamina much reduced in fertile part); receptacle of sorus columnar with sporangia all round it, indusium ultimately a shallow uniform cup; stem massive, erect; cubical cells scattered (1 sp., Juan Fernandez Is)ThyrsopterisTribe Culciteae. Fertile and sterile parts of frond not greatly dimorphous; receptacle of sorus fused to inner indusium (as in Dicksonia)', inner indusium thinner than outer, the two slightly joined together at the base; stem prostrate or erect; cubical cells in a continuous layer as in DicksoniaCulcita
Conspectus of the family Cyatheaceae: new comments:

I would now raise the subfamilies to the rank of family, but see no reason for other changes. PICHI SERMOLLI () includes all in the order Dicksoniales, with suborders and families thus:
  • Thyrsopteridineae: Thyrsopteridaceae (Thyrsopteris).
  • Culcitineae: Culcitaceae (Culcita).
  • Dicksoniineae: Dicksoniaceae (including Cibotium and Cystodium), Lophosoriaceae (Lophosoria).
  • Cyatheineae: Cyatheaceae (Sphaeropteris, Alsophila, Nephelea, Trichopteris, Cyathea, Cnemidaria).
  • Metaxyineae: Metaxyaceae (Metaxya).

Cytology

Chromosome numbers in the genera Dicksonia, Culcita and Cibotium have been recorded by Manton () and in Cyathea by Manton & Sledge () and by Manton (); Prof. Manton also permits me to report unpublished observations on Culcita and Dr T. G. Walker on Cnemidaria. No observations are yet available for Thyrsopteris, Lophosoria, Metaxya and Cystodium. The numbers are: Dicksonia, n = 65 (3 spp.); Cibotium, n = 68 (2 spp.); Cyathea, n = 69 (several spp.); Cnemidaria horrida, n = 69; Culcita macrocarpa, n = 66 approx.; Culcita dubia, n = 58.