Diselma archeri
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| Hook. f. |
Diselma archeri is a conifer and the only species of the monotypical genus Diselma from the cypress family (Cupressaceae). Their distribution area is in the highlands in the west of the island of Tasmania south of Australia. The species is not considered endangered.
description
Diselma archeri forms evergreen dioecious shrubs or small trees with heights of 1.5 to 4 m, rarely trees up to 6 m high or prostrate specimens. The trunk reaches a diameter of 30 to 40 m, but remains mostly slimmer. The bark is rough and scaly, initially brown and later gray. The inner bark is reddish brown. The branches are short and stiff, they form a dense crown.
leaves
The leaves grow tightly pressed on numerous, dense, straight, more or less stiff branches 10 to 20 mm long, which have a diameter of 1.5 mm and a square, more rarely triangular cross-section. The leaves are cross opposite, less often in whorls of three. They are overlapping, rhombic, keeled, with entire margins with a blunt end, 1 to 2 mm long and 0.6 to 1.5 mm wide and resemble scales. The stomata are arranged in two short, whitish bands near the base of the leaf. Young leaves on mature branches are initially reddish and later turn green to olive green.
Cones and seeds
The numerous, 3 mm long pollen cones stand individually at the ends of the branches. 6 to 8 triangular-deltoid microsporophylls are formed per cones , which are smaller than the leaves. Usually only four of them are fertile, whereby these develop two pollen sacs. The seed cones are also at the ends of the branches and mature within a year to small, 3 mm long and 2 mm wide cones with two cross-opposed pairs of cone scales. Each of the upper scales usually bears 2, sometimes 3 seeds in its armpit . The brown seeds are flattened ovoid and have 2 to 3 seed wings. A distinct columella is formed at the end of the cone. Mature cones are 2 to 3 mm long and 1 to 1.5 mm wide. They are the smallest coniferous cones in the southern hemisphere and probably the smallest coniferous cones of all.
Distribution and ecology
The distribution area of Diselma archeri is in the highlands in western Tasmania , but the species is absent in the northwest of the island. They can be found at altitudes of 550 to 1400 meters in subalpine and alpine heather bogs and scree fields, sometimes along rivers and on the edges of lakes and ponds. Where it grows along with perennials and small shrubs such as Astelia alpina , microstrobos niphophilus , Microcachris tetragona , the Podocarpus Podocarpus lawrencei , the ericaceous Richea scoparia and Richea pandanifolia , various lomatia species, acicularsi Orites and Orites revoluta , various straw types of flowers ( Helichrysum ) and Leptospermum species, but also with larger shrubs and small trees such as the cypress-like scaly spruce ( Athrotaxis cupressoides ), Phyllocladus aspleniifolius , the beech Nothofagus gunnii and Eucalyptus coccifera . It prefers acidic, often wet, flat peat soils. Precipitation is heavy, with frost and snow all year round. The snow cover can last for several months.
In the Red List of the IUCN is diselma be deemed not at risk ( "Lower Risk / least concern"). It is pointed out, however, that a new check of the risk is necessary. The species is widespread in the highlands but can be endangered by fire.
Systematics and research history
Diselma is the only type which therefore monotypic genus Diselma from the family of cypress plants (Cupressaceae). It was first described in 1857 by Joseph Dalton Hooker in his Flora Tasmaniae . In 1880 she was also known under the synonym Fitzroya archeri (Hook.f.) Benth. & Hook.f. assigned to the genus Fitzroya . The generic name Diselma chosen by Hooker is derived from the Greek word di for "two" and selma for " upper deck " and refers to the two pairs of seed scales per seed cone. The specific epithet archeri honors the botanist William Archer (1820–1874), who explored the flora of Tasmania.
The leaves resemble those of the type occurring in the same habitat Microcachrys tetragona from the family of podocarpaceae (Podocarpaceae), the cross alternate leaf arrangement of equivalent Microcachrys not the usual spiral of the family but is similar to the blade position of diselma . The Sporophylle of the pins of both sexes but in contrast to Diselma spirally arranged.
use
The species is rarely cultivated, but it is traded for horticultural use and can be found in botanical gardens. The species grows slowly and is used especially in rock gardens . The cultivar Read Dwarf grows even more slowly and has young, light green leaves.
proof
literature
- Aljos Farjon: A Handbook of the World's Conifers . tape 1 . Brill, Leiden-Boston 2010, ISBN 90-04-17718-3 , pp. 361-362 .
Individual evidence
- ↑ a b c d e f g Farjon: A Handbook of the World's Conifers , Volume 1, p. 361
- ^ Armin Jagel, Veit Dörken: Morphology and morphogenesis of the seed cones of the Cupressaceae - part III. Callitroideae . Bulletin of the Cupressus Conservation Project, Vol. 4 (3), 2015, pp. 91-103 ( PDF )
- ↑ a b c Farjon: A Handbook of the World's Conifers , Volume 1, p. 362
- ↑ Diselma archeri in the endangered Red List species the IUCN 2011. Posted by: Conifer Specialist Group, 1998. Accessed December 3, 2011th
- ↑ Diselma archeri. In: Germplasm Resources Information Network (GRIN). United States Department of Agriculture, accessed December 3, 2011 .
- ↑ Fitzroya archeri. In: The Plant List. Retrieved December 4, 2011 .
Web links
- Diselma archeri. In: The Gymnosperm Database. Christopher J. Earle, December 12, 2010, accessed December 26, 2011 .
- Diselma archeri. Australian National Botanic Gardens, accessed December 3, 2011 .