|Photo Ken Hill
|The Cycad Pages
- Cycas nathorstii J. Schust., "Pflanzenr. 99: 76, fig. 10e" (1932).
- "TYPE: Sri Lanka, 1866, Thwaites 3689 in Herb. Barbey-Boisser (holo G (photo NSW); iso A, K, LE, P)."
Honouring Swedish palaeobotanist Alfred Gabriel Nathorst (1850-1921),
professor at the Natural History Museum in Stockholm.
The upland cycad from Sri Lanka has been generally known as C.
circinalis (Trimen 1898), and was in fact one element of the
protologue of the latter (Linnaeus 1753; Fl. Zel.). German historian
and sometime botanist Julius Schuster distinguished this taxon
in 1932 on the basis of specimens collected by Thwaites and distributed
to European herbaria by Swiss botanist and philanthropist William
Barbey-Boissier (1842-1914). Schuster's work has been largely
(rightly) ignored, including this taxon, although, in this case,
a valid distinction exists. Collection detail cited was
"Ceylon: Thwaites 1866 n. 3689 in Herb. Barbey-Boissier."
The Barbey-Boissier herbarium and types are in G, including this
specimen. This may not have been the specimen examined by Schuster,
as it has no annotation by him and was filed as undetermined.
Schuster's types were mainly in B, and were destroyed during WW2.
This sheet includes both leaflets and megasporophylls, and has been
designated the lectotype. George Thwaites (1812-1882) was superintendent
of the Royal Botanic Garden at Peradeniya in Ceylon from 1849-1880,
and his main collections are now in K and PDA.
De Laubenfels and Adema (1998) included C. nathorstii in the
synonymy of C. sphaerica, but also placed some Sri Lankan
collections of the same taxon in C. circinalis.
Distinguished from C. circinalis and C. sphaerica of the
Indian mainland by the more robust habit, wider leaflets and larger male
cones with longer and more curved apical spines on microsporophylls.
Megasporophyll apices of C. nathorstii are narrowly triangular
with numerous fine lateral spines extending almost to the very tip,
whereas the Indian species possess broader apices with a distinct
extended apical spine that is free from lateral teeth. C. nathorstii
is distinguished from C. zeylanica, the other species occurring in
Sri Lanka, by the more closely spaced and more chartaceous leaflets, the
shorter, softer and less pilose cataphylls and lack of spongy endocarp.
Distribution and habitat:
Known only from Sri Lanka, where it occurs in inland and
upland forests in the north of the island, usually in somewhat drier sites.
Still locally frequent, although not in great numbers, this species
is regarded as vulnerable.
Red List status VU ?A2c.
Leaves bright green, semiglossy, 160-180 cm long, flat (not keeled) in section (opposing leaflets inserted at 180° on rachis), with 140-170 leaflets, tomentum shedding as leaf expands. Petiole 45-55 cm long (25-30% of total leaf), petiole glabrous, spinescent for 90-95% of length. Basal leaflets not gradually reducing to spines.
Median leaflets simple, weakly discolorous, 190-310 mm long, 9-14 mm wide, narrowed to 3-4 mm at base (to 25-35% of maximum width), 17-20 mm apart on rachis; median leaflets section flat; margins flat; apex softly acuminate, not spinescent; midrib raised above, raised below.
Cataphylls narrowly triangular, soft, thinly sericeous or lacking tomentum, 50 mm long, persistent.
Pollen cones narrowly ovoid, orange; microsporophyll lamina firm, not dorsiventrally thickened, 30-40 mm long, 15-22 mm wide, apical spine prominent, gradually raised, 10 mm long.
Megasporophylls 15-30 cm long, brown-tomentose; ovules 6-10, glabrous; lamina lanceolate, 40-65 mm long, 18-25 mm wide, obscurely dentate, with 26-40 pungent lateral spines 1-4 mm long, 1 mm wide, apical spine distinct from lateral spines, 10-14 mm long.
Seeds flattened-ovoid; sarcotesta yellow; fibrous layer present; sclerotesta smooth. Spongy endocarp absent.