Blechnum pacificum
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| Blechnum pacificum | ||||||||||||
| Lorence & ARSm. |
Blechnum pacificum is a plant from the genus of blechnum ( Blechnum ) within the family of blechnaceae (Blechnaceae). It occurs on some islands in the southern Pacific .
description
Blechnum pacificum grows as a large fern . It forms an upright or almost upright, seldom lying, short rhizome , which is covered with scales at the top and is between 1 and 2 centimeters thick without the scales. The thin, light brown to brown scales on the rhizome and on the base of the fern fronds are linear-subtle to oblong-ovate, with a length of 2 to 3 centimeters and a width of 1 to 5 millimeters. They are usually thicker at their base and in the middle, making them appear a little darker in color. The scale base is rounded to truncated, the tip is curved and the scale edges are whole or almost whole.
The fronds are arranged in tufts at the ends of the rhizomes. The 41 to 102 cm long fronds usually have either fertile or infertile pinnate leaves on their 0.4 to 1 cm thick and strong stalks , but occasionally both forms are found together on one frond, with the infertile always on the base of the frond and the fertile at the tip of the frond. The light to dark brown frond stalks are furrowed on the top. Their base is densely covered with scales, the density of which decreases towards the tip, so that they can also be completely absent there.
The simple-pinnate, infertile fronds are seldom 35 to, usually 50 to 100 centimeters in length and rarely 20 to, usually 30 to 60 centimeters wide, elongated-ovoid to elongated-elliptical and consist of 19 to 30 pairs Leaflets and a single leaflet at the tip of the frond stem. In young fronds, the main axis and the leaf veins are scab-like covered with thin brown to pale brown, oblong-egg-shaped to sub-shaped scales, which can be up to 1 centimeter long. The somewhat leathery to leathery leaflets are stiff, have a straw-colored to dark brown leaf axis and are pointed at the tip. The leaflets in the lower area of the fern frond stand on a stalk up to 2 millimeters long and are arranged opposite to each other, while the almost opposite to alternate leaflets in the upper frond area are sessile and often fused with the main axis of the frond. The leaflet at the tip of the frond resembles the other leaflets in the upper frond area. The leaflets in the middle frond area are the largest and are linearly shaped with a length of 11 to 30 centimeters and a width of 1.5 to 2.5 centimeters. At the oblique-wedge-shaped base of each leaflet there is a slightly swollen, glandular pneumathode , while the leaf edge is serrated and the tip is pointed or serrated.
The fertile fronds are almost the same size or slightly smaller than the infertile fronds and consist of up to 40 pairs of leaflets. The fertile leaflets are about the same length as the infertile, but are significantly narrower with a width of 2.5 to 5 millimeters. The leaf margins are strongly bent back and the underside of the leaf, with the exception of the green leaf base, is covered over a large area with linearly shaped sori , while the upper side is smooth.
The approximately ellipsoidal spores are approximately 67 micrometers long and around 47 micrometers thick, with 8 to 12 micrometers per perispore .
Occurrence
The natural range of Blechnum pacificum is on the islands of the southern Pacific . It includes Rapa Iti Island , which belongs to the Austral Islands , the Society Islands Moorea , Raiatea and Tahiti and the Marquesas Islands Hiva Oa , Fatu Hiva , Nuku Hiva , Tahuata and Ua Pou .
Blechnum pacificum thrives at altitudes of 380 to 1500 meters. The species is found in the lowlands, in moderately humid to damp forests, in bushland, in valleys, on slopes and mountain ridges and on rocky river banks. There it grows mainly in clearings or in shady locations. On the Marquesas, Blechnum pacificum is often associated with Crossostylis biflora , Dicranopteris linearis , Freycinetia impavida , Metrosideros collina , Pandanus tectorius , Santalum insulare and other native tree and shrub species as well as other vascular spore plants .
Systematics
It was first described as Blechnum pacificum in 2011 by David H. Lorence and Alan Reid Smith in PhytoKeys , number 4, page 8. The occurrences of the species were previously included in Blechnum capense . The specific epithet pacificum indicates the natural distribution area in the Pacific .
Blechnum venosum , which is native to the island of Rapa Iti , is the closest related species .
swell
- David H. Lorence, Warren L. Wagner, Kenneth R. Wood, Alan R. Smith: New pteridophyte species and combinations from the Marquesas Islands, French Polynesia . In: PhytoKeys . No. 4 , 2011, ISSN 1314-2003 , p. 5-51 , doi : 10.3897 / phytokeys.4.1602 .
Individual evidence
- ↑ a b c d e f g h i David H. Lorence, Warren L. Wagner, Kenneth R. Wood, Alan R. Smith: New pteridophyte species and combinations from the Marquesas Islands, French Polynesia . In: PhytoKeys . No. 4 , 2011, ISSN 1314-2003 , p. 5-51 , doi : 10.3897 / phytokeys.4.1602 .
- ↑ Blechnum pacificum. In: The International Plant Names Index. www.ipni.org, accessed February 4, 2015 (English).
