| 翻訳と辞書 |
Macivera
''Macivera'' is a genus of extinct vascular plants. Fossils were found in sediments in Bathust Island, Nunavut, Canada, from the upper Silurian (Ludfordian, around ). The leafless stems (axes) branched dichotomously and were relatively thin, being between 0.7 and 1.0 mm wide. Spore-forming organs or sporangia, which were elliptical, being longer than wide, were borne on the end regions of stems. ''Macivera'' is considered to be a zosterophyll.〔
==Description==
The genus was first described from a small number of specimens found in sediments in Bathurst Island, Nunavut, Canada, which are considered to be of Late Silurian age (Ludfordian, around ).〔
Stems (axes) were smooth, devoid of leaves, hairs or other protrusions, and were between 0.7 and 1.0 mm wide〔 (around the lower limit of the size Boyce suggested as being compatible with the presence of vascular tissue〔), tapering down to 0.1 mm towards the apex of those stems which did not bear sporangia. The stems branched equally and dichotomously, with some suggestion of downwards branching at the base. The overall height of the plant is estimated to be some 8 cm.〔
Spore-forming organs or sporangia were borne towards the end of stems, apparently in clusters, angled slightly away from the upright. They were either borne directly on the stem or had short stalks, and do not appear to have been arranged into distinct rows. Sporangia were elliptical in shape, 1.3 to 2.0 mm high and 1.1 to 1.3 mm wide, so that they were longer than wide. As is typical of zosterophylls, they split to release their spores via a linear opening at the opposite end to their attachment to the stem. Spores were found, around 50 µm in diameter, but may have been immature; they were of one size range (i.e. the plant was homosporous).〔
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
■ウィキペディアで「Macivera」の詳細全文を読む
スポンサード リンク
| 翻訳と辞書 : 翻訳のためのインターネットリソース |
Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.
|
|