Sabal Adans., Fam. Pl. 2: 495 (1763)

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Number of Taxa

  • 15 species

Discussion

Biology And Ecology

Common Name

Etymology

Diagnosis

  • Single-stemmed fan palms of the Caribbean and neighbouring mainland of Central and North America, usually with conspicuously costapalmate leaves with unarmed petioles that have a triangular cleft at the base. The highly branched inflorescences bear solitary hermaphroditic flowers and usually rather small blackish fruit. (J. Dransfield, N. Uhl, C. Asmussen, W.J. Baker, M. Harley and C. Lewis. 2008)

Description

  • Dwarf, moderate or tall, usually robust, solitary, acaulescent or erect, unarmed, pleonanthic, hermaphroditic palms. Stem often descending shortly and recurved, covered with leaf bases, rough, striate, and obscurely ringed, or becoming ± smooth, grey, and bare with age. Leaves induplicate, marcescent, shortly to prominently costapalmate; sheath later with a conspicuous cleft below the petiole, margins fibrous; petiole often very long, channelled adaxially, rounded abaxially, sometimes bearing caducous indumentum; adaxial hastula short and truncate, or usually elongate and acute or acuminate, margins sharp, abaxial hastula sometimes distinguishable as a low ridge; blade flat to mostly arched, divided along the central abaxial fold to the middle or nearly to the costa, further divided along adaxial folds into drooping linear, ± even, rarely uneven, single-fold segments, briefly to rather deeply bifid, sometimes filiferous, segments with midribs prominent abaxially, interfold filaments sometimes present, glaucous or not, sometimes paler beneath, often with caducous indumentum along the major ribs, midribs prominent, transverse veinlets obscure or conspicuous. Inflorescence shorter, as long as or longer than the leaves, interfoliar, branching to 4 orders; prophyll short, 2-keeled, 2-lobed; peduncular bracts several, tubular below with a conspicuous, short to long and narrow tip, variously caducously tomentose; rachis equalling or longer than the peduncle; rachis bracts like peduncular bracts, decreasing in size distally; bracts of the second and third order well developed, tubular, decreasing in size distally; prophylls present on most branches; rachillae slender, with spirally arranged bracts, each subtending a low spur branch bearing a solitary flower. Flowers symmetrical; calyx somewhat thickened at the base, tubular, shallowly 3-lobed, often prominently nerved when dried; corolla tubular below, lobes elliptic, slightly imbricate in bud, spreading to suberect with incurved membranous margins at anthesis, becoming strongly inrolled when dry; stamens 6, the filaments rather fleshy, flattened, united in a tube about as high as the calyx, adnate up to the mouth of the corolla tube, then distinct and awl-shaped, not inflexed at the apex, anthers erect in bud, dorsifixed, ± versatile or erect, narrowly elliptic, latrorse; carpels 3, completely connate, ovarian part trilobed and only slightly broader than the elongate 3-grooved style, stigma capitate, trilobed, papillose, ovule basal, anatropous. Pollen ellipsoidal, slightly asymmetric; aperture a distal sulcus; ectexine tectate, finely to coarsely perforate, or perforate and micro-channelled, aperture margin similar or slightly finer; infratectum columellate; longest axis 33–50 µm; post-meiotic tetrads usually tetrahedral, sometimes tetragonal or, rarely, rhomboidal [8/16]. Fruit usually developing from 1 carpel, sometimes from 2 or 3, globose to pyriform, stigmatic scar and abortive carpels basal; epicarp smooth, mesocarp fleshy without fibres, endocarp thin, membranous. Seed free from endocarp, shining brown, depressed-globose, usually concave below when dry, raphe and hilum basal, endosperm homogeneous with a shallow intrusion of seed coat; embryo lateral or subdorsal. Germination remote-ligular; eophyll entire, elongate. Cytology: 2n = 36. (J. Dransfield, N. Uhl, C. Asmussen, W.J. Baker, M. Harley and C. Lewis. 2008)

Anatomy

Relationships

Taxonomic accounts

Fossil record

  • There are many fossil records for costapalmate leaves; they are the earliest type of fossil palm leaves recovered to date. The leaves are usually described under the fossil genus Sabalites, even though there are a number of other modern, predominantly coryphoid, genera, that have costapalmate leaves. The re-circumscription of Sabalites by Read and Hickey (1972) embraces any palmate leaf, ‘with a definite costa or extension of the petiole into the blade’, whereas Palmacites is recommended for palm-like leaves that are, ‘pure palmate, lacking a costa or extension of the petiole into the blade’. New fossil genera for costapalmate leaves, Costapalma, and for palmate leaves, Palustrapalma, were published by Daghlian (1978), but these genera have not been widely adopted. Other Sabal-like fossils include small monosulate pollen grains and, rarely, leaf cuticle and fruits. The fossil genus Sabalites is not only used frequently as a generic name for costapalmate leaves but also applied to fruits. The oldest record of Sabalites appears to be S. carolinensis Berry (Berry 1914b) from the Upper Cretaceous (Coniacian-Lower Santonian Black Creek Formation [Middendorf arkose member] of South Carolina [USA]); this is also the oldest palm fossil assignable below family level. Sabalites magothiensis (Berry) Berry (Berry 1905, 1911) from the Santonian of Maryland and New Jersey (USA) and S. longirhachis (Unger) J. Kvac˘ek and Hermann (Hermann and Kvac˘ek 2002; Kvac˘ek and Hermann 2004) from the Lower Campanian of Austria are somewhat younger. Other Upper Cretaceous records include, from North America (Wyoming), S. eocenica (originally described from an Eocene location) and S. montana (Dorf 1942); and fragments of a large fan leaf, Sabalites sp. (Berry 1919a), from Tennessee (Ripley Formation). An incompletely preserved costapalmate leaf, S. ooaraiensis, (Ôyama and Matsuo 1964) is described from the fluvial deposits of the Upper Cretaceous Ôarai flora on the coast of Naka-gawa. From the Palaeocene onwards, records of costapalmate leaves become more frequent and widespread. In North America, records for the Rocky Mountains and Great Plains have been reviewed by Brown (1962), whereas records for the Middle and Upper Eocene floras of southeastern North America were reviewed by (Berry 1924) and also by Daghlian (1978). Details of leaf venation, adaxial and abaxial epidermal cells and stomatal cell arrangement allowed Daghlian (1978) to make direct comparison between the Eocene Sabal dortchii Daghlian and the modern genus. Other Tertiary records come from Europe: southern England (Palaeocene) (Reid and Chandler 1933, Chandler 1961b, 1961c, 1962, 1963); France, Tertiary (Saporta 1865); Germany, Upper Eocene–Miocene (Mai and Walther 1978), Miocene (Van der Burgh 1984); Switzerland, Upper Oligocene (Büchler 1990); Czech Republic, Miocene (Kva˘cek 1998); and Hungary, Oligocene (Andreánszky 1949). A relationship with the fossil Sabal major Unger was suggested for the inflorescence and rachilla of Tuzsonia hungarica (Andreánszky 1949), based on associated palm leaf fragments. However, the pollen described from individual flowers is probably too small, and the exine pattern unlike that of modern Sabal pollen. A number of Tertiary records have also been found: in Russia, Caucasus, Middle Miocene (Takhtajan 1958); Kamchatka Peninsula, Eocene (Budantsev 1979); and Transcaucasia, Oligocene (Akhmetiev 1989; leaf and associated monosulcate pollen); and in India, a leaf axis (Trivedi and Verma 1981) from the Deccan Intertrappean of Madhya Pradesh (although the age span of these volcanic deposits is controversial; see Chapter 5). Four species of Sabalites leaves are reported from the Tertiary of China (Peking Institute of Botany, and Nanjing Institute of Geology and Palaeontology 1978) and, from the Eocene of Japan, leaf fragments have been recorded from lignite mines in Hokkaido: Sabalites nipponica (Kryshtofovich 1918). Subfossil fragments of clasping petiole bases and seeds (‘stones’) are reported by Berry (1917) from the Pleistocene of Vero (Florida). Fossil fruits are reported from southern England, Lower Eocene as Sabal grandisperma (Reid and Chandler 1933); and Germany (Geiseltal), Eocene as S. bracknellense (Mai 1976). Few dispersed monosulcate fossil palm-like pollen can be confidently assigned to Sabal. This is because the pollen of many genera in tribes Sabaleae, Cryosophileae, Trachycarpeae and Chuniophoeniceae share similar size ranges and exine characteristics. Records include Sabalpollenites sp. from the Eocene of North America (Tennessee) (Potter 1976), Sabal sp. from the Lower Eocene of southern England (Khin Sein 1961), and three new Miocene species of finely reticulate Sabalpollenites from the Czech Republic (Konzalova 1971) (this association is questionable because the exine of Sabal pollen tends to be finely to coarsely perforate, or perforate and micro-channelled). There are also records from the Lower Miocene of Poland (Macko 1957) and from the Tertiary of China (Sabalpollenites areolatus; Song et al. 1999). (J. Dransfield, N. Uhl, C. Asmussen, W.J. Baker, M. Harley and C. Lewis. 2008)

Uses

Bibliography

  • Dransfield, J. , Uhl, N. , Asmussen, C. , Baker, W.J. , Harley, M. & Lewis, C. 2008. Genera Palmarum. The evolution and classification of palms. Kew Publishing, Royal Botanic Gardens Kew.