Etymology:
From the Latin circinus, a spiral, in reference to the
inrolled leaflets in developing leaves.
Literature: Gaudichaud 1829, Trimen 1898, Stapf 1916, Leandri 1931, Ho & Duong 1960, Raizada & Sahni 1960, Suvatabandhu 1961, Smitinand 1971, Zamora & Co 1986, Hill 1994 Illustrations: Bot. Mag. 1828 Griffith 1854 (and as C. jenkinsiana), Schuster 1932 (and as C. rumphii ssp. zeylanica), Miquel 1842, Warburg 1900, Smitinand 1971, Smitinand 1972, Zamora & Co 1986 Historical notes: Surrounded by confusion since its inception, this was described as the single constituent species when the great Swedish botanist Carolus Linnaeus established the genus Cycas in 1753. He had, however, based his description on a number of earlier works that in fact covered at least three distinct species as we now know them. The subsequent history of this name has been one of total confusion. C. circinalis has subsequently appeared in the literature more frequently than any other Cycas combination, arguably without a single author wholly correctly applying the name. Of the eight references cited by Linnaeus, only two refer to C. circinalis as now typified. This reflects an increasing understanding of the systematics of the group since the time of Linnaeus' work. The other species covered by Linnaeus' description are now known as C. revoluta, separated by Thunberg in 1784, and C. rumphii, separated by Miquel in 1839. The latter is part of a widespread species complex, all of which have been treated as part of C. circinalis at some time or other. Although well known in Indian culture for many centuries (Rheede 1682), the first reference to this species in Western writings was in Rheede's Hortus Malabaricus, published in Amsterdam in 1682. Although this publication has generally been accepted as the basis for this species (de Candolle 1868: 525, Stapf 1916, Wijnands 1986), it was not formally designated the type until 1993 (Jarvis et al.). Much of the confusion associated with this species arises from the difficulty in recognising Miquel's segregate species C. rumphii, and its full geographic extent. Miquel himself had difficulty recognising the limits of these taxa (1868), and often changed his mind (see C. rumphii). Characteristics by which these species can be recognised were also not well known. The difficulty in separating the two has continued to the present (eg. Jones 1993), and has severely reduced the usefulness and value of a number of anatomical and morphological studies based on unvouchered or cultivated materials (eg. Dehgan & Yuen 1983, Pant 1993). Almost all plants in cultivation that have been known as C. circinalis in fact belong to the C. rumphii complex. The name C. circinalis has also been applied uncritically to local in many parts of the world, without real knowledge of the true nature of typical C. circinalis. Examples of misapplication occur in Ceylon (Trimen 1898 - C. nathorstii), Thailand (Suvatabandhu 1961, Smitinand 1971, 1972 - C. spp.), Malaysia ( Gibbs 1914 - C. rumphii), The Philippines ( Amoroso 1986, Foxworthy 1911, Zamora & Co 1986 - C. riuminiana), New Guinea (Borrell 1986 - C. apoa; Paijmans 1986 - C. campestris; White 1922 - C. scratchleyana) and the western Pacific (Burkill 1901, de Laubenfels 1978, Hemsley 1895, Yuncker 1959 - C. seemannii; Fosberg & Sachet 1975, Stone 1970 - C. micronesica). In the protologue of C. circinalis, Linnaeus (1753, 1754) cited treatments of Cycas from eight earlier works, including at least three taxa as they are currently circumscribed, but also stated 'Habitat in India'. Stapf (1916) stated '... the C. circinalis of India represented by Rheede's Todda Panna (Rheede 1682: 9, tab. 13-21), the accepted basis of Linnaeus's species.' Lectotypification was discussed but not formally designated by Wijnands (1986). No specimens relating to Hortus Malabaricus are known, and one of the series of illustrations of Todda Panna by Rheede (tab. 19) has since been designated the lectotype by Stevenson in Jarvis et al. (1993). Distinguishing features: Characterised by a non-pectinate megasporophyll with subglobular seeds that display a distinctive fibrous layer within the sarcotesta, and an attenuate microsporophyll apex. This megasporophyll morphology occurs in many other species, and largely the cause of much of the confusion. The attenuate microsporophyll state is, however, restricted to a few species from the Indian subcontinent, as is the fibrous layer within the sarcotesta. This fibrous layer is a distinct advanced evolutionary character found in all species of the Indian subcontinent, and also in the C. pectinata group and in a number of upland forest species occurring throughout South-east Asia. Distribution and habitat: C. circinalis is now known to be an Indian endemic, restricted to the Western Ghats, in the states of Kerala, Karnataka, Tamil Nadu, and the south of Maharashtra. It typically occurs in fairly dense, seasonally dry scrubby woodlands in hilly areas. Many trees in this habitat lose their leaves in the dry season, and C. circinalis is also facultatively deciduous in extremely dry times. The taxon from the northern Eastern Ghats in the state of Orissa, described as C. circinalis var. orixensis by Haines (1924) and generally treated as C. circinalis, differs markedly in its megasporophylls. It in fact represents a separate species (see C. spherica). Conservation status: Locally abundant in several areas, although the habitat has been severely reduced and degraded. Good populations still exist in a number of forests reserves. Vernacular: Indu. Description:
Stems arborescent, to 5 m tall. Leaves bright green, semiglossy, 150-250 cm long, flat (not keeled) in section (opposing leaflets inserted at 180° on rachis), with 170 leaflets, tomentum shedding as leaf expands. Petiole 40-70 cm long, glabrous, spinescent for 90% of length. Basal leaflets not gradually reducing to spines. Median leaflets simple, weakly discolorous, 150-300 mm long, 7-12 mm wide, narrowed to 2.5 mm at base, 12 mm apart on rachis; median leaflets section flat; margins flat; apex softly acuminate, not spinescent; midrib raised above, flat below. Cataphylls narrowly triangular, soft, thinly sericeous or lacking tomentum, 50 mm long, persistent. Pollen cones narrowly ovoid, orange, 45 cm long, 10 cm diam.; microsporophyll lamina firm, not dorsiventrally thickened, 38-50 mm long, 12-19 mm wide, apical spine prominent, gradually raised, 25 mm long. Megasporophylls 30 cm long, brown-tomentose; ovules 4-10, glabrous; lamina lanceolate, 74-100 mm long, 25-38 mm wide, regularly dentate, with 24 pungent lateral spines, apical spine distinct from lateral spines. Seeds subglobose, 25-38 mm long; sarcotesta yellow; fibrous layer present; sclerotesta smooth. Spongy endocarp absent.
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