Dioon purpusii
Dioon purpusii
Dioon purpusii is a representative of cycads ( Cycadales ) and belongs to the genus Dioon. The species is named after the botanist Carl Albert Purpus ( 1851-1941 ).
Features
The tribes are tree shaped and erect, in older specimens also bent due to the weight of the trunk and crown. They are available individually or in groups on the basis of Wurzelschösslingen. The stem is 1-5 meters high with a diameter of 25 to 40 cm. The Cataphylle are 7-8 cm long, 1.5 to 2 cm wide and densely pubescent.
The many leaves are stiff, upright, in old plants sometimes curved downwards and backwards. They are 0.8 to 1.6 m long, 16 cm wide, flat or slightly keeled in young plants. Young leaves are densely pubescent, the hairs remain on stalk, rachis and the underside of leaves. The petiole is 5-20 cm long, slightly square, has a swollen, 2-3 cm wide basis. The leaflets are available in 75 and 130 pairs, are stiff, pungent and facing forward. They are 7 to 11.5 cm long, 8-10 mm wide, and wrong attached to the rachis: pointing towards the blade tip side is higher. In the upper part of the leaf blades overlap at the bottom of the leaflets are further away. The leaf margin is entire or occupied with small thorns.
The female cones are individually, initially upright, inclined slightly later. They are ovoid, 44 to 52.5 cm in length and 20 to 25 cm in diameter near the base. The stem is short, so that the pin appears sitting. The lying on the journal surface side of the sporophyll is long triangular, from 10 to 18,5 cm high, at the base of 5 to 9.5 cm wide, densely woolly. The sarcotesta of the seed is the ripe yellow. The Sklerotesta is nearly spherical, 30-40 mm long, 29-30 mm in diameter and smooth. The chalaza has a 4 to 5 mm wide pit.
The male cones are individually and maintained until the pollen is widespread. They are 20 to 36 cm long with a diameter of 7 to 13 cm. The handle is short, 2 to 5 cm long; the journal appears mostly sitting. The lying on the journal surface side of the sporophyll is triangular, 15-22 mm high as wide, gray - green and densely hairy light brown at the tap point. The sporangia are in two groups, separated by a 2 mm wide sterile zone.
Dissemination and locations
The species is endemic in the Mexican state of Oaxaca, where it occurs in Tomellin Canyon near the villages of Santa Catarina and Tomellin as well as in the Sierra Mixteca. The locations are in dry, tropical laubwerfendem forest, mostly in the shade of trees. They usually grow on the steep rocky slopes of deep ravines along with cacti, agaves and Beaucarnea in 1000 up to 1500 m above sea level. The annual rainfall is 500 to 1000 mm and falls mainly in the summer. The temperatures in the summer 20 to 30 ° C, in the winter 10-20 ° C.
In this area, it occurs in individual- rich colonies scattered over the area. The area is relatively inaccessible. Locations and plants are hardly disturbed, the local population uses only the leaves on Palm Sunday.
Botanical history
The species was first collected in 1901 and initially held for Dioon edule. 1908 Joseph Nelson Rose and Daniel T. MacDougal they gathered again and recognized it as a separate species, the Rose 1909 purpusii described as Dioon. By 1980, however, were all examples of the genre that have leaf edge - thorns, called Dioon purpusii, since several other species have been described.
Documents
- 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 Add: Contributions from the United States National Herbarium. Vol 12, 1909, ISSN 0097-1618, pp. 259-302, digitized.