Dioon purpusii
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Dioon purpusii |
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Dioon purpusii is a member of the cycads (Cycadales) and belongs to the genus Dioon . The species is named after the botanist Carl Albert Purpus (1851–1941).
features
The trunks are tree-shaped and upright, in older specimens they are also curved due to the weight of the trunk and crown. They stand individually or in groups due to root saplings. The trunk becomes 1 to 5 meters high with a diameter of 25 to 40 cm. The cataphylls are 7 to 8 cm long, 1.5 to 2 cm wide and densely hairy.
The numerous leaves are stiff, upright, sometimes curved downwards and backwards in old plants. They are 0.8 to 1.6 m long, 16 cm wide, flat or slightly keeled in young plants. Young leaves are densely hairy, the hairs remain on the stem, rachis and underside of the leaflets. The petiole is 5 to 20 cm long, slightly square, has a swollen base 2 to 3 cm wide. The leaflets stand in 75 to 130 pairs, are stiff, piercing and directed forward. They are 7 to 11.5 cm long, 8 to 10 mm wide, and attached to the rachis at an angle: the side facing the tip of the leaf is higher. In the upper part of the leaf the leaves overlap, in the lower part the leaves are further away. The leaf margin is entire or covered with small thorns.
The female cones stand individually, initially upright, later slightly inclined. They are egg-shaped, 44 to 52.5 cm long and 20 to 25 cm in diameter near the base. The stem is short so that the cone appears seated. The lying on the side of the journal surface sporophyll is long triangular, from 10 to 18,5 cm high, 5 cm wide at the base to 9.5, densely woolly. The sarcotesta of the seed is yellow at maturity. The sclerotesta is approximately spherical, 30 to 40 mm long, 29 to 30 mm in diameter and smooth. The chalaza has a 4 to 5 mm wide pit.
The male cones stand solitary and upright until the pollen has spread. They are 20 to 36 cm long with a diameter of 7 to 13 cm. The stem is short, 2 to 5 cm long; the cone usually appears seated. The side of the sporophyll lying on the cone surface is triangular, 15 to 22 mm high and wide, gray-green and densely hairy light brown at the cone tip. The sporangia are in two groups, separated by a 2 mm wide sterile zone.
The number of chromosomes is 2n = 18.
Distribution and locations
The species is endemic to the Mexican state of Oaxaca , where it occurs in the Tomellin Canyon near the villages of Santa Catarina and Tomellin and in the Sierra Mixteca. The locations are in dry, tropical deciduous forest, mostly in the shade of trees. Usually they grow on the steep rocky slopes of deep gorges together with cacti , agaves and Beaucarnea at 1000 to 1500 m above sea level. The annual rainfall is 500 to 1000 mm and falls mainly in summer. Temperatures are 20 to 30 ° C in summer and 10 to 20 ° C in winter.
In this area it occurs in colonies with a large number of individuals that are scattered across the area. The area is relatively inaccessible. Locations and plants are hardly disturbed, the local population only uses the leaves on Palm Sunday .
Botanical history
The species was first collected in 1901 and initially thought to be Dioon edule . In 1908 Joseph Nelson Rose and Daniel T. Mac Dougal collected them again and recognized them as a separate species, which rose described in 1909 as Dioon purpusii . Until 1980, however, all specimens of the genus that have leaf margin thorns were called Dioon purpusii , since then several other species have been described.
literature
- Loran M. Whitelock: The Cycads. Timber Press, Portland OR 2002, ISBN 0-88192-522-5 , pp. 168 f.
- Joseph Nelson Rose : Studies of Mexican and Central American Plants. No. 6. In: Contributions from the United States National Herbarium. Vol. 12, 1909, ISSN 0097-1618 , pp. 259-302, digitized .
Individual evidence
Web links
- Dioon purpusii on the Cycad Pages of the Royal Botanic Gardens Sydney.
- Dioon purpusii inthe IUCN 2013 Red List of Threatened Species . Posted by: Chemnick, J., Gregory, T. & Morales S., 2009. Retrieved April 28, 2014.