Anatomical Studies of Cyathea and Trichipteris (Cyatheaceae)

Abstract

Comparative anatomical studies of the mature stems of two species each of Trichipteris and Cyathea (Cyatheaceae) are described. The outermost boundary of the stem is typically a two‐layered hypodermis. Mucilage‐sac cells are randomly distributed in all parenchymatous areas of the stem and form articulated laticifer systems. Localized areas of sclerenchyma tissue occur in the cortex of both T. microphylla and C. suprastrigosa. All species studied possess medullary bundles, whereas cortical bundles are found only in T. trichiata. Accessory bundles occasionally are associated with indentations in the internal stelar sheath of T. trichiata. The stelar pattern in each genus is a dictyostele and consists of individual meristeles. Distinctive cubical cells typically occur wherever sclerenchymatous fibers and parenchyma cells abut one another. Tangential cells occur within the primary phloem of each meristele, and occasionally within the larger accessory bundles. The primary xylem of the adventitious roots is typically diarch, although triarch and tetrarch xylem may occur. Leaf traces and petiole strands are similar anatomically to the accessory bundles. Based upon this study Trichipteris and Cyathea show striking anatomical similarities, and appear to be closely‐related taxa.

New cyathealean tree fern, Yavanna chimaerica gen. et sp. nov., from the Early Cretaceous of Livingston Island, Antarctica

“…The other genera included in the family share the absence of medullary bundles, contrasting with the Cyatheaceae and the studied specimens. Cyatheacean tree ferns are dictyostelic, with numerous, small medullary bundles, and dissected vascular strands in the petiole bases (Lucansky and White, 1974;Lucansky, 1977), contrasting with the solenostelic stem of Yavanna, which presents few bigger medullary bundles, and one or three-parted petiole vascular strands.…”

“…In particular, the presence of medullary bundles links the new species with both Cyatheaceae and Thyrsopteridaceae. In cyatheacean ferns, medullary bundles fuse with the margins of the meristeles in the leaf gaps (Lucansky, 1977), whereas in Thyrsopteris, a medullary bundle acts as a compensation strand (sensu Bower, 1926), filling the leaf gap. In the studied specimens, it was impossible to determine the behavior of the medullary bundles in Yavanna chimaerica.…”

“…2B) which may suggest that these bundles act also as a compensation bundle. Another feature that differs between Thyrsopteridaceae and Cyatheaceae is the presence of scales in the latter taxon, whereas Thyrsopteris has bristle hairs as epidermal appendages (Lucansky, 1977;Nishida, 1984). Unfortunately, it was impossible to determine with confidence if the indument of Yavanna is composed by hairs or scales, due to preservation quality of the fossils.…”