Culcita
Content
Distribution
Africa: Madeira (Madeira present), Asia-Tropical: Borneo present; Jawa (Jawa present); New Guinea present; Philippines (Philippines present), Australasia, Azores present, Lesser Sunda Is present, Malaysia present present, N. Celebes present, New Caledonia present, New Hebrides present, Pacific: Fiji (Fiji present); Samoa (Samoa present), Solomon Islands present, Southern America: Argentina Northeast (Formosa absent), tropical America present
Subg. Culcita: Madeira and Azores, tropical America. Subg. Calochlaena: Australia, New Caledonia, New Hebrides, Fiji, Samoa, Solomon Islands, Malaysia; in Malaysia: Java, Lesser Sunda Is, Borneo, N. Celebes, Philippines, New Guinea. The species C. formosae (Chr.) Maxon, of Formosa, appears to be a Dennstaedtia, as originally placed by Christ.
Taxonomy
The genus Culcita, as first fully assembled by Maxon, consists of two distinct parts, subg. Culcita and subg. Calochlaena Maxon. The former includes only two very closely related species, C. macrocarpa Pr. and C. coniifolia (Hook.) Maxon; subg. Calochlaena includes several species in a quite different geographic area which includes part of Malaysia. The species of this subgenus have much smaller sori than those of subg. Culcita, and were not regarded as part of the genus until Diels (1899) included C. straminea (Labill.) and Copeland (1908, 1909) C. dubia (R. Br.) () and C. javanica (Bl.) in it under the name of Balantium. John Smith (1875), who recognized Balantium as distinct from Dicksonia, had placed C. straminea in Dennstaedtia. C. dubia remained doubtfully in its original genus Davallia, and C. javanica doubtfully in Dennstaedtia, in Christensen's Index Filicum (1905).
The genus Culcita differs strikingly from Dicksonia in the shape of the frond, which always has a long stipe and is more finely divided, with all major parts triangular in outline and asymmetric at the base. It differs also from Dicksonia in the grooves of the upper surface of all axes, including midribs of leaflets, being open to reeeive grooves of minor axes. In both these characters, Culcita agrees with Thyrsopteris. The difference in rachis-characters between Dicksonia and Culcita is exactly that between Ctenitis and Dryopteris.
Culcita differs from Dennstaedtia in its more massive rhizome which is sometimes erect and when creeping has a radially symmetrical vascular system (dorsiventral in Dennstaedtia) with overlapping leaf- gaps; also in the inner indusium not being appreciably joined to the outer along its sides (the two are partly or almost wholly united in Dennstaedtia, forming a cup or funnel) but joined to the receptacle of the sorus on its basiscopic side as in Dicksonia (the receptacle is free or columnar in Dennstaedtia). As regards rachis-characters, species like both Dicksonia and Culcita are at present placed in Dennstaedtia (see , who makes this distinction the main division in his key to American species of Dennstaedtia).
Subg. Calochlaena, to which Malaysian species belong, might possibly rank as a separate genus, but it appears to be much more nearly related to subg. Culcita than to any other ferns. Apart from size of sorus, subg. Culcita differs from subg. Calochlaena in the shape and size of pneumathodes, and in the shape of the vascular strands as seen in transverse section near the base of the stipe; in the latter character subg. Calochlaena conforms closely to the general scheme of Dicksonia and Cyathea, whereas in subg. Culcita the vascular strands on the adaxial side diverge instead of converging and curving inwards.
The genus Culcita differs strikingly from Dicksonia in the shape of the frond, which always has a long stipe and is more finely divided, with all major parts triangular in outline and asymmetric at the base. It differs also from Dicksonia in the grooves of the upper surface of all axes, including midribs of leaflets, being open to reeeive grooves of minor axes. In both these characters, Culcita agrees with Thyrsopteris. The difference in rachis-characters between Dicksonia and Culcita is exactly that between Ctenitis and Dryopteris.
Culcita differs from Dennstaedtia in its more massive rhizome which is sometimes erect and when creeping has a radially symmetrical vascular system (dorsiventral in Dennstaedtia) with overlapping leaf- gaps; also in the inner indusium not being appreciably joined to the outer along its sides (the two are partly or almost wholly united in Dennstaedtia, forming a cup or funnel) but joined to the receptacle of the sorus on its basiscopic side as in Dicksonia (the receptacle is free or columnar in Dennstaedtia). As regards rachis-characters, species like both Dicksonia and Culcita are at present placed in Dennstaedtia (see , who makes this distinction the main division in his key to American species of Dennstaedtia).
Subg. Calochlaena, to which Malaysian species belong, might possibly rank as a separate genus, but it appears to be much more nearly related to subg. Culcita than to any other ferns. Apart from size of sorus, subg. Culcita differs from subg. Calochlaena in the shape and size of pneumathodes, and in the shape of the vascular strands as seen in transverse section near the base of the stipe; in the latter character subg. Calochlaena conforms closely to the general scheme of Dicksonia and Cyathea, whereas in subg. Culcita the vascular strands on the adaxial side diverge instead of converging and curving inwards.