Studies in the Phytogeny of the Filicales III.On Metaxya and certain other relatively primitive Ferns

1974

Comparative studies of the nodal and vascular anatomy in the monotypic genera Metaxya and Lophosoria are discussed as they relate to the taxonomy and phylogeny of the Cyatheaceae. Both genera are distinctive and primitive with respect to habit, stem and petiole indument, stelar pattern, and nodal anatomy. Metaxya possesses a prostrate, dorsiventral rhizome, whereas a short, upright radial stem occurs in Lophosoria. Trichomes occur on the stems and leaf petioles of these genera. Both Metaxya and Lophosoria have a spiral phyllotaxy, and adventitious buds occur on the petiole bases. The stelar pattern is basically a siphonostele, although frequently a dictyostele is found in Lophosoria. Accessory bundles are lacking in both genera. A characteristic petiole pattern is found in these genera, with an increase in complexity from an undivided strand in Metaxya to the three-parted petiole pattern in Lophosoria. Data from nodal and vascular anatomy indicate that these taxa are distinct from the other genera in the Cyatheaceae and belong in an independent position at the base of the Cyatheoid line, although in some respects an affinity to members of the Dicksoniaceae is indicated.

mentioning

confidence: 63%

mentioning

confidence: 98%

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

See 3 more Smart Citations

Comparative Studies of the Nodal and Vascular Anatomy in the Neotropical Cyatheaceae. I. Metaxya and Lophosoria

1974

Comparative Studies of the Nodal and Vascular Anatomy in the Neotropical Cyatheaceae. Ii. Squamate Genera

1974

Vascular tissue development in the mature stems of the six squamate genera (those with scales as stem and petiole indument) of the Cyatheaceae is described. All squamate genera possess an erect stem, although Cnemidaria approaches an acaulescent condition. The majority of the species studied possesses a spiral phyllotaxy, although a whorled condition predominates in certain species. Adventitious roots arise from the leaf bases and, at irregular intervals, from the stem. Adventitious buds occur in the genera Alsophila and Nephelea and show the same ontogenetic changes as occur in the young sporophytes of tree ferns. Mature stems have a dictyostele with overlapping leaf gaps; this consists of individual meristeles, each surrounded by sclerenchymatous tissue. All genera possess medullary bundles, whereas cortical bundles are found only in certain genera and species. The origin, course, and function of these accessory vascular bundles are discussed. The squamate genera in the Cyatheaceae show striking similarities in both anatomical and morphological characters, and constitute a natural grouping.

Comparative Ontogenetic Studies in Young Sporophytes of Tree Ferns. I. A Primitive and an Advanced Taxon

White

1976

Ontogenetic studies of young sporophytes were undertaken to determine anatomical and morphological differences between a primitive (Lophosoria quadripinnata) and an advanced (Sphaeropteris elongata) tree fern. In both species the first leaf is simple, fanshaped, and possesses dichotomous venation. Later‐formed leaves exhibit either a pinnate or bipinnate pattern of laminar dissection. As the sporophyte matures, the stelar pattern changes from a protostele to an amphiphloic siphonostele, and finally to a dictyostele in Sphaeropteris. Medullation of the protostele occurs either prior to or after the formation of the first leaf trace in both species. Differentiation of xylem in the shoot is acropetal and the appearance of mature protoxylem occurs closer to the apical meristem in Sphaeropteris. The nodal pattern varies within each species with a no gap 1‐trace pattern characteristic for the first two or three leaves, depending upon the taxon. In Lophosoria subsequent leaves possess a unilacunar 1‐trace nodal pattern, whereas a complete nodal series (1 gap 1‐trace to 1 gap 6‐trace) occurs in Sphaeropteris. Fusiform leaf gaps are noted in both species. The shoot apical meristem is dominated by a single apical cell, with an organized apical cell first found in P2. Stem, root, and petiole anatomy are discussed.