10.-下石炭世石化茎、叶柄新属&早期蕨类植物分类综述

P. Barnard, J. G. Long
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引用次数: 37

摘要

tradidioxylon gen. 11 .为石化茎和叶柄而竖立,其中初生木质部具有三放射状,在臂端和中部具有原木质部。次生木质部致密,由小管胞组成,在所有壁上有多列的有棱的小坑。光线又窄又高。皮层有硬化巢和放射状纤维带(sparganum结构)。在模式种T. primaevum sp. nov.中,叶柄在直径约1cm(或更大)的茎上以1 / 3的层状螺旋形生长,相距5 - 6cm。叶柄在其基部肿胀(直径约8毫米),在轴处逐渐变细至约2毫米,未见二裂。叶柄到第一穗的长度可超过10厘米。松树交替升起,它们自己也长出了分支。t形的叶柄束在每根臂的末端有两个原木质部群,中央的原木质部在轴上分为三个。在Lyginorachis属中发现了两个不能确定为原生木的分离轴,命名为L. whitadderensis sp. 11 .它们的t形维管束略大于原生木的轴,横臂的末端较宽,可能具有三个原木质部群。原生木和白石斛的茎条都有交替的三角羽状纹,但白石斛的茎条也有一对亚相对的君主羽状纹。虽然在原裸子植物科中与无性植物有一定的亲缘关系,但在蕨类植物中,三钩梭梭与布钩梭梭一起被分类为布钩梭梭。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
10.—Triradioxylon—a New Genus of Lower Carboniferous Petrified Stems and Petioles together with a Review of the Classification of Early Pterophytina
Synopsis Triradioxylon gen. nov. is erected for petrified stems and petioles in which the primary xylem has a triradiate form and possesses protoxylem at the ends of the arms and in the central region. Secondary xylem is dense and composed of small tracheids having multiseriate bordered pits on all walls. Rays are narrow and high. The cortex has sclerotic nests and radial bands of fibres (sparganum structure). In the type species T. primaevum sp. nov. the petioles are borne 5–6 cm apart in a phyllotactic spiral of ⅓ on a stem about 1 cm (or more) diameter. The petiole is swollen at its base (about 8 mm diameter) and very gradually tapers to about 2 mm in the rachis which has not been seen to dichotomise. The length of petiole up to the first pinna may exceed 10 cm. Pinnae arose alternately and themselves branched. The T-shaped petiolar bundle has two protoxylem groups at the end of each arm and the central protoxylem divided into three in the rachis. Two detached rachises which cannot be assigned with certainty to Triradioxylon primaevum are placed in the genus Lyginorachis and named L. whitadderensis sp. nov. In these the T-shaped vascular bundle is slightly larger than that in the rachises of T. primaevum and the ends of the transverse arms are wider and may possess three protoxylem groups. The rachises in both T.primaevum and L. whitadderensis bear alternate triarch pinna-traces but in L. whitadderensis a pair of sub-opposite monarch pinna-traces is also present. Triradioxylon is classified along with Buteoxylon in the family Buteoxylonaceae placed tentatively as incertae sedis in the Pteridosperms although showing some affinity with Aneurophyton in the Progymnospermopsida.
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