Reconstructing the Pennsylvanian-Age Filicalean Fern Botryopteris tridentata (Felix) Scott

Numerous anatomically preserved fragments of the Middle Pennsylvanian age filicalean fern, Botryopteris tridentata, occur in coal balls collected at the Pittsburgh and Midway Coal Company mine near Baxter Springs, Kansas. Included are the first fertile specimens of the species, evidence of complete vegetative frond architecture, and fronds that are specialized for vegetative propagation. Rhizomes are erect and unbranched, have helical phyllotaxis and short internodes, and typically display an ectophloic solenostele. Fronds are tripinnately compound with lobed pinnules that have open, dichotomous venation. Fertile pinnae or individual pinnules are interspersed among vegetative frond segments and produce sori of annulate sporangia beneath veins on the abaxial pinnule surface. Fertile pinnule lobes are rolled toward the abaxial surface to enclose the sori. Sporangia have a horizontally elongated biseriate annulus located near the short broad stalk and produce tetrahedral-shaped trilete spores with coarse spines. Epiphyllous branches diverge from the stipe or rachis, and some fronds produce only branches. This fern is reconstructed as having short stems. Helically arranged fronds are either pinnately dissected with lobed vegetative pinnules and abaxially rolled fertile pinnules or are specialized for vegetative propagation. The latter functioned as the foliar equivalent of stolons. While some characters of the B. tridentata plant are similar to those of Botryopteris forensis, generitype of the Botryopteridaceae, others are more comparable to those of Psalixochlaena cylindrica, generitype of Psalixochlaenaceae, suggesting the need for reevaluation of systematic relationships among species of the Botryopteridaceae and Psalixochlaenaceae.     

QUAESTORA AMPLECTA GEN. ET SP. N., A STRUCTURALLY SIMPLE MEDULLOSAN STEM FROM THE UPPER MISSISSIPPIAN OF ARKANSAS

A well preserved, permineralized seed fern stem is described from the Upper Mississippian Fayetteville Formation of north central Arkansas. Quaestora amplecta gen. et sp. n. is 41.6 cm long and exhibits six pairs of decussate, highly decurrent petiole bases. The stem has a cruciform, exarch protostele with prominent secondary xylem, vascular cambium and secondary phloem. Leaf traces are terete and occur as an outer ring with a small number of internal strands. The cauline vasculature, leaf-trace production, petiolar anatomy and several other features indicate that this specimen represents the most structurally simple and geologically ancient medullosan stem presently recognized.     

VASCULAR CONNECTION BETWEEN LATERAL ROOTS AND STEM IN THE OPHIOGLOSSACEAE

The vascular connection between lateral roots and stem in the Ophioglossaceae and in two leptosporangiate fern species was examined. Two types of connections were found: “gradual” connections, which resemble leaf traces in ontogeny and morphology, and “abrupt” connections, which resemble the connections between lateral roots and their parent roots. Gradual root-stem connections occur in the genera Ophioglossum and Helminthostachys and in Woodwardia virginica. They are initiated in shoot apices distal to the level where cauline xylem elements mature. They resemble leaf traces in being provascular (procambial) strands that connect the cauline stele with the future vasculature of lateral appendages. As with leaf traces, gradual connections are part of the provascular and, later, protoxylem continuity between stems and lateral appendages. Gradual connections have many features in common with leaf traces, and the term root trace is applicable to them. The order of radial maturation of the primary xylem in gradual connections varies in different parts of the connections. It is endarch near the intersection with the cauline stele and exarch where the connections intersect root steles. Gradual connections resemble the transition regions of certain seed plants where protoxylem is also continuous from stem to root and the order of maturation is found to change continuously from stem to root. Abrupt connections occur in Botrychium and Osmunda cinnamomea. They develop in shoot apices at levels where cauline xylem is mature or maturing. The mature xylem does not dedifferentiate, so provascular and protoxylem continuity of the kind found in root traces does not occur. Also, reorientation of the order of maturation does not occur in abrupt connections. Xylem connectors are found in the region where radially oriented elements of the connections abut the longitudinally oriented cauline elements. Abrupt connections resemble the connection of secondary roots with their parent root systems since xylem connectors and the lack of continuity are also features found in these vascular systems. The resemblance of the vascular pattern of the fern root trace to the transition region of seed plants suggests that the radicle is more closely comparable to the cladogenous roots of pteridophytes than hitherto supposed.     

CAULINE VASCULATURE AND LEAF TRACE PRODUCTION IN MEDULLOSAN PTERIDOSPERMS

Medullosa and Sutcliffia specimens from the Paleozoic of North America and Europe are examined to determine the architecture of the cauline vasculature and mode of leaf trace production. Emphasis is placed on the identification and characterization of protoxylem strands and their relationship to leaf trace production. Organization of the primary xylem varies from a single protostele to a dissected stele composed of two to many more or less independent bundles. In Medullosa the bundles of primary xylem are each surrounded by secondary xylem, forming separate segments of vascular tissue (‘steles’ of previous workers). These vascular segments may divide and fuse at different levels in the stem. A definite number of protoxylem strands occur near the periphery of the primary xylem. The protoxylem strands divide at intervals producing protoxylem to the departing leaf traces. Leaf traces thus formed arise from all the vascular segments in a coordinated and predictable way and pass outward through emission areas in the secondary xylem. This type of cauline vascular architecture is compared to that of other seed plants. The vascular system of Medullosa stems is interpreted as a dissected monostele. Sympodial vascular architecture has apparently evolved from a protostele separately within the medullosan pteridosperms.     

Todea from the Lower Cretaceous of western North America: implications for the phylogeny, systematics, and evolution of modern Osmundaceae

The first fossil evidence for the fern genus Todea has been recovered from the Lower Cretaceous of British Columbia, Canada, providing paleontological data to strengthen hypotheses regarding patterns of evolution and phylogeny within Osmundaceae. The fossil consists of a branching rhizome, adventitious roots, and leaf bases. The dictyoxylic stem has up to eight xylem bundles around a sclerenchymatous pith. Leaf traces diverge from cauline bundles in a typical osmundaceous pattern and leaf bases display a sheath of sclerenchyma around a C-shaped xylem trace with 2-8 protoxylem strands. Within the adaxial concavity of each leaf trace, a single sclerenchyma bundle becomes C-shaped as it enters the cortex. The sclerotic cortex is heterogeneous with an indistinct outer margin. The discovery of Todea tidwellii sp. nov. reveals that the genus Todea evolved by the Lower Cretaceous. A phylogenetic analysis combining morphological characters of living and extinct species with a previously published nucleotide sequence matrix confirms the taxonomic placement of T. tidwellii. Results also support the hypothesis that Osmunda s.l. represents a paraphyletic assemblage and that living species be segregated into two genera, Osmunda and Osmundastrum. Fossil evidence confirms that Osmundaceae originated in the Southern Hemisphere during the Permian, underwent rapid diversification, and species extended around the world during the Triassic. Crown group Osmundaceae originated by the Late Triassic, with living species appearing by the Late Cretaceous.     

Conantiopteris schuchmanii, gen. et sp. nov., and the Role of Fossils in Resolving the Phylogeny of Cyatheaceae s.l.

Conantiopteris schuchmanii gen. et sp. nov. The specimen, 23.2 cm long and 11.7 cm wide, shows helically arranged persistent frond bases embedded in adventitious roots, and is clothed by multicellular trichomes. A parenchymatous pith with mucilaginous cells and sclerotic nests is surrounded by an amphiphloic distyostele, parenchymatous inner cortex, and outer sclerenchymatous cortex. Sclerenchyma also surrounds the cauline vasculature and leaf traces. Medullary and cortical bundles are absent. Phloem contains both axially elongated and tangential sieve elements. Frond bases are oval in outline with three vascular bundles, including an undulating abaxial arc and an adaxial pair. Protoxylem of the stipe is endarch and is associated with cavity parenchyma. These characters are indicative of tree fern affinities. A cladistic analysis using trunk characters of both living and fossil tree ferns was conducted to help establish relationships of the new species and other fossil ferns, and to test hypotheses of general tree fern relationships. Additional analyses of living taxa only were also performed. Results from the analysis using both living and fossil taxa compare favorably with those that included only living species when either morphological characters or molecular sequences of the chloroplast gene rbcL are utilized. Although there are variations in the topologies of the various trees, results indicate that the new genus is nested among a paraphyletic assemblage of dicksoniaceous, lophosoriaceous, and metaxyaceous species that subtend a monophyletic Cyatheaceae s.s. Received 26 April 1999/ Accepted in revised form 15 July 1999     

Cyathea cranhamii sp. nov. (Cyatheaceae), anatomically preserved tree fern sori from the Lower Cretaceous of Vancouver Island, British Columbia

Permineralized cyatheaceous sori occur among remains of conifers, fungi, and other plants in newly discovered calcareous concretions from Early Cretaceous (Barremian) marine sediments of Vancouver Island, British Columbia, Canada. Sori are superficially attached in two rows to narrow pinnules and display a globose sphaeropteroid indusium. Annulate sporangia with multicellular stalks diverge from a basal, vascularized receptacle. The nearly vertical uniseriate annulus is not interrupted by the stalk. The sporangia bear 64 trilete spores with perispore sculpturing that ranges from irregular granulate/echinate to prominent rodlets. These specimens, described as Cyathea cranhamii sp. nov., are the first anatomically preserved tree fern sori from the fossil record. They represent the most ancient evidence for fertile structures of the Cyatheaceae and demonstrate that essentially modern species of cyatheaceous tree ferns had evolved by the Early Cretaceous.     

ORIGIN AND EARLY MORPHOGENESIS OF LATERAL BUDS IN THE FERN DAVALLIA

The general organography, vascular organization, and leaf and bud development in Davallia solida and D. trichomanoides are described. These epiphytic species have creeping shoots with dorsally-borne leaves in a distichous phyllotaxis and the buds occur near each leaf base. Roots are borne on the ventral and flanking surfaces of the rhizome, but only at bud positions. The vascular pattern of these species is a perforated solenostele. Leaf and bud traces have distinctly different origins. While the proximity of buds to leaves has suggested that bud origin is axillary, observations show that the origin of buds is cauline and that their position is extra-axillary from inception. The stages of structural morphogenesis in Davallia buds differ significantly from the scheme proposed by Wardlaw. The principal difference is the absence of a resting period occurring between the origin and continued development of buds in Davallia. The elongated internodes which separate leaf-bud pairs from one another, the topographically distinct and predictable positions of leaves and buds, the structural equivalence of unexpanded buds, and vascular differences in leaves and buds make Davallia an useful species for physiological studies of differential bud expansion.     

XYLEM ANATOMY,WATER FLOW,AND HYDRAULIC CONDUCTANCE IN THE FERN CYRTOMIUM FALCATUM

Xylem anatomy and water relations were studied in holly fern (Cyrtomium falcatum, Aspidiaceae) to determine the details of the pathway for water flow through an entire plant and the influence of tracheid number and lumen diameter on water flow. Each leaf has two adaxial traces and an abaxial trace, which are supplied by diarch adventitious roots attached to the dictyostele of the rhizome near the leaf base. Anatomical observations and dye experiments showed that each adaxial bundle vascularizes the approximately seven pinnae on its side of a leaf. An abaxial bundle is intermittently connected to an adaxial bundle as well as other abaxial bundles, forming a minor vascular pathway between the bundles of the leaf axis. Changes in both number and diameter of tracheids result in an acropetal decrease in hydraulic conductance per unit length along the rachis, although tracheid number locally increases when the trace for a pinna is produced in an adaxial bundle. Water flow was determined from the transpiration distal to the point in question or by forcing a solution through an axis with applied pressure. The water potential gradient along the plant axis was quite constant, indicating that hydraulic conductance per unit length varied with leaf area to be supplied. About 40% of the overall water potential drop occurred from the rachis into the pinnae, which reflected factors controlling water potential gradients in the lamina and not a very low conductance in the petiolule xylem. Hydraulic conductances calculated using the Hagen-Poiseuille equation and tracheid diameters were generally double those of measured conductances. Since the values tended to vary by a constant factor, tracheid number and diameter may largely control water flow in the xylem.     

Vascular Organization and some Aspects of the Morphology of the Rhizome of Gymnogrammitis dareiformis

Gymnogrammitis dareiformis, the taxonomically controversialdavalliaceous fern has a parenchymatous rhizome, in the groundtissue of which groups of 1–16 thick-walled cells (withpeg-like protrusions on inner walls) are irregularly scattered.Paleae clothing the rhizome are basally attached, gland-tippedand bearing unicellular marginal hairs. The vascular cylinderis a radially-symmetric dictyostele dissected by spirally-arrangedleaf gaps into slender reticulated meristeles. Some of the dorso-laterallyplaced leaves alone are fully developed; most other leaves aresuppressed and some are highly reduced (the larger reduced leavesappear as protrusions on the rhizome and have a well-formedleaf base). The leaf trace of developed as well as the largerreduced leaves is a channel-shaped loose reticulum of four vascularstrands; the trace of the reduced leaves is smaller and endsblindly at the leaf base. The leaf trace of the smaller reducedleaves is vestigial and represented often by only a pair ofvascular strands fusing into one and ending blindly in the cortexof the rhizome. The leaf trace of suppressed leaves fuses backwith the stelar cylinder, forming a convex reticulum bridgingthe sides of the leaf gap. It is suggested that the characteristic stelar organizationof the Davalliaceae is derived by suppression of leaves froma radiallysymmetric dictyostele with spirally-arranged leafgaps as found in Nephrolepis and that Gymnogrammitis with itsreduced and suppressed leaves indicates the process of transition.The creeping solenostelic rhizome with two-ranked leaf arrangementcould be derived from an erectgrowing dictyostelic one by supppressionof leaves.     

SHOOT VASCULAR SYSTEM AND PHYLLOTAXIS OF CASUARINA (CASUARINACEAE)

In species of Casuarina with multileaved whorls, each stem vascular bundle divides radially into two at the site of a leaf trace separation, and the same two bundles rejoin acropetally to where the trace supplies a leaf. Such divisions are divisions of a single vascular bundle, and the rejoining of bundles forms a single bundle. Proposals that the extant primary vascular systems of dicotyledons may have been derived as in conifers are incorrect in so far as Casuarina is concerned, or the system has evolved beyond that so far proposed for dicotyledons. Reasons are offered, however, for considering that fernlike leaf gaps are not present. Leaf traces supply leaves at the first nodes distal to their origins. The ways by which an increase or decrease of stem bundles occur are described. Phyllotactic patterns range from helical (rare) to whorled. In the embryo, where leaves occur decussately, of certain species with multileaved whorls, and in the shoot apices of species with tetramerous whorls, slight differences in the levels of leaf attachments and the bending of leaf traces indicate the probable evolution of extant whorled phyllotaxies from one or more helical arrangements. Stages in the evolution are suggested. The leaves in most species with multileaved whorls are in true whorls. The original periderm of branchlets lies internally to the internodal traces and chlorenchyma, but is otherwise external to the vascular system. It is concluded that each leaf originates at its level of separation from the axis despite several structural features suggesting that the leaf bases have become congenitally adnate to the stem.     

Stem structure and its bearing on the systematics of Pleurothallidinae (Orchidaceae)

STERN, W. L., PRIDGEON, A. M. & LUER, C. A., 1985. Stem structure and its bearing on the systematics of Pleurothallidinae (Orchidaceae) . Pleurothallids comprise a subtribe of numerous orchids consisting of mostly diminutive New World epiphytes. The cauline system involves a branching rhizome bearing unifoliate ramicauls. The inflorescence usually originates from an adaxial invagination toward the apex of the ramicaul. Two or more cycles of vascular bundles traverse the ramicaul; typically, there is an outer, branching series of smaller strands and an inner, non-branching series of larger strands. In the ultimate internode subtending the leaf the smaller, outer bundles migrate between the larger, inner bundles and become aggregated in the medullary region. They bend adaxially to vascularize the inflorescence. The leaf is articulated at an abscission layer to the prolongated apex of the ramicaul more or less distal to the cauline invagination. In some pleurothallids, a cauline annulus appears at the insertion of the inflorescence and cither below or at the attachment of the leaf to the apex of the ramicaul. Anatomical studies show that the annulus is the external manifestation of an intercalary meristem. Except for Pleurothallis , genera are consistent in having or lacking an annulus. Genera with two pollinia either possess or lack the annulus; those with four to eight pollinia always lack the annulus. It is suggested that the intercalary meristem is a derived characteristic providing survival value and a selective advantage to those pleurothallids in which it occurs. Presence of the intercalary meristem is correlated with other structural features considered to represent specializations.     

CONTRIBUTIONS TO THE MORPHOLOGY OF LEPTOCHILUS AND PARALEPTOCHILUS

Nayar , B. K. (Natl. Bat. Gard., Lucknow, India.) Contributions to the morphology of Leptochilus and Paraleptochilus. Amer. Jour. Bot. 50(4): 301–308. lllus. 1963.—Morphology of L. axillaris and P. decurrens is described; L. axillaris is epiphytic, possessing a wide creeping, soft, parenchymatous rhizome, covered sparsely by peltate paleae, while P. decurrens is rupicaulous, with a short, brittle rhizome having slender sclerenchyma strands and densely covered by basally attached paleae. The vascular cylinder of the rhizome is dictyostelic and composed of a large number of closely placed, thick, vascular bundles with characteristic, thickened, endodermal cells in L. axillaris; it is dictyostelic and composed of a few, slender, distantly placed vascular strands in P. decurrens. Leaf traces are multiple strands which in P. decurrens originate in alternate succession from either side of the dorsal median vascular bundle of the rhizome, but in L. axillaris, from the lateral vascular bundles of the rhizome. The branch traces are paired strands which are lateral in the former and medianly placed in the latter. Scattered sclerenchyma strands occur in the stipe of P. decurrens. Paraphyses are absent in P. decurrens, but filamentous paraphyses occur in L. axillaris. The spores are bilateral and smooth-walled in both, and the prothalli are of the branched, ribbonlike type developing as in Colysis. Prothalli are naked in L. axillaris, but bear sparse mammillate marginal hairs in P. decurrens.     

Contributions to the Morphology of Some Species of Microsorium

Morphology of eleven epiphytic and rupicaulous species of Microsoriumis described. The paleae in the genus are either peltate withthe basal region developing secondarily as a hood over the stalk,or basally attached with auricles on either side of the stalk.The auricles in M. hancockii and M. pteropus develop from singleinitial cells adjacent to the stalk, while in the others nospecialized initial cells occur. Marginal and terminal glandularhairs occur on the paleae, except in M. hancockii and M. pteropusin which marginal hairs are absent. Slender sclerenchyma strands are scattered profusely in theground tissue of the rhizome. The stelar cylinder is dictyostelicand is dissected by lacunae into cylindrical vascular bundles.Leaf traces are multiple strands originating as branches fromthe dorsal median vascular bundle of the stelar cylinder andthe one next to it on each side. Two or three closely placedvascular bundles of the rhizome constitute the vascular connexionto each branch of the rhizome. Venation of the leaf lamina is reticulate with most of the free-endingveinlets entering foliar hydathodes. The juvenile leaves bearhairs similar to the pro-thallial hairs and are spatulate witha medianly placed forked vein. Sori are generally punctiform,but in M. hancockii and M. pteropus spread slightly over theveins, often forming elongated coenosori. Uniseriate (multiseriatein M. rubidum), multicellular paraphyses occur in all speciesexcept M. scolopendria. The spores are monolete and either psilateor granulate. The prothalli develop from 3-5 cells long germ filaments inwhich the anterior cells divide longitudinally and form an ameristicprothallial plate. An apical meristematic cell is formed later,and a cordate prothallus is developed, except in M. hancockiiand M. pteropus in which a definite meristem is never formedand the prothalli are ribbon-shaped and branched. The cordateprothalli possess polypodiaceous hairs: the ribbon-shaped onesare more or less naked and devoid of any midrib. The chromosome number in the species is n = 36 (zn = 72).     

蜈蚣草的解剖结构与组织化学特征

蜈蚣草（Pteris vittata）是多年生的超积累砷植物,并用于修复受重金属污染的土壤。利用光学显微镜和荧光显微镜来研究蜈蚣草的解剖结构及组织化学特征,以此明确该物种适应干旱岩生环境,以及具有离子超富集作用的特点。结果表明（：1）蜈蚣草孢子体的根状茎、不定根和叶的结构均为初生结构,不定根的结构由内而外包括维管柱、内皮层、皮层、木质化厚壁组织层和表皮。（2）根状茎结构由内而外包括网状中柱、内皮层、皮层、表皮外覆盖的角质层。（3）羽状复叶的总叶柄的结构由内而外包括维管束、内皮层、皮层、厚壁组织层、表皮外覆盖的角质层。叶片为异面叶,表皮内方具厚壁层,叶表皮具角质层,仅下表皮有气孔。（4）蜈蚣草根表皮、皮层与根毛的表面富含果胶,皮层木质化;黄连素离子通透性试验结果显示,根毛、根表皮和皮层滞留大量黄连素离子。综上,植物体的内皮层、木质化厚壁组织层、异面叶和厚的角质层结构说明蜈蚣草适应岩生环境,根具木质化皮层和富含果胶的组织化学特点,以及离子通透性试验表明其与离子超积累功能有关。     

On the systematic position of Athyrium crenulato-serrulatum Makino from North-eastern Asia

The fern Athyrium crenulato-serrulatum Makino is found in the whole of Northeastern Asia embracing Northeastern China, Korea, Japan, Ussuri and the Far East USSR. It is similar to the European Athyrium distentifolium, formerly known as A. alpestre, in having exindusiate round or ovate sori, but differs in several essential characters, such as the well-spaced fronds are biseriately arranged along a thick and long-creeping rhizome, the base of stipe is thickened and not attenuated towards the point of attachment, the deltoid-ovate lamina with the basal pinnae as long as those next above, which all are distinctly petiolate and the rachis, costis and especially the costules of pinnules clad in fine pale-colored generally septate hairs underneath. All these clearly show that the fern in question is not an Athyrium sen. str. neither Pseudoathyrium Newman to which latter the fern was referred by Nakai. However, we have been long suspicious of its proper systematic position. In his recent monograph on the genus Cornopteris (Acta Phytotax. Geobot. 30: 104. 1979.) Kato has pointed out that C.crenulato-serrulata (Makino) Nakai “has the northernmost destribution in the genus and exhibits a few characteristics similar to Athyrium, the swollen base of stipes with projections and cartilaginous lamina margin. By these characteristics the species is clearly discriminated from other species”. According to Kurita (1964), Mitui (1970) and Karo (1978) the species in question has chromosome numbers n=40, the base number of the subfamily Athyrioides instead of x=41, the base number of the subfamily Diplazioides including Cornopteris Nakai. Since thefern in question fits no other athyrid genera, hence a new genus is proposed.     

Oligocene ferns from the Rancahué Formation (Aluminé, Neuquén, Argentina): Cuyenopteris patagoniensis nov. gen., nov. sp. (Polypodiales: Blechnaceae/Dryopteridaceae) and Alsophilocaulis calveloi Menéndez emend. Vera (Cyatheales: Cyatheaceae)

The study of abundant permineralized fern remains collected in the Oligocene Rancahué Formation (Neuquén Province, Argentina) allowed the identification of two different taxa. The name Cuyenopteris patagoniensis nov. gen., nov. sp. is proposed for several stems and fronds characterized by the presence of caulinar dictyosteles with root gaps, producing C-shaped leaf traces composed by two hippocampiform bundles flanked by eight to ten small round bundles, half of them diverging from cauline meristeles and the rest from the hippocampiform bundles. The presence of these features, along with frond bases with adaxial grooves and a pair of pneumatophores, suggest affinities with the Blechnaceae or Dryopteridaceae. The second identified taxon is Alsophilocaulis calveloi Menéndez. Based on features observed in these new materials, including characteristics of the mantle of adventitious roots and anatomy of the petiole bases, an emended diagnosis for this latter species is proposed.     

Size and reproduction of Thelypteris limbosperma and Athyrium distentifolium along environmental gradients in Western Norway

The performance of the ferns Thelypteris limbospgrma and Athyrium distentifolium , as expressed by number of son on pinnules and frond size, has been related to environmental gradients. Data have been collected from homogenous fern-dominated stands from different geographical areas in Western Norway. Number of sori produced, which was assumed to indicate fern fertility, was highly variable. There were significant correlations between frond size and fertility, but only 35–46 % of the variation in fertility could be explained by differences in frond size. The highest number of sori was found on plants of medium size, and for A. distentifolium there was a statistically significant reduction in sori number on fronds taller than 125 cm. For the linear relationships between fertility and size, it is suggested that the small X-intercept and slope defines the high competitive ability of A. distentifolium in sites with a long-lasting snow cover. The ferns may dominate in large stands even though their fertility is low or zero, which indicates that they under certain ecological conditions mainly reproduce vegetatively. Both ferns show decreased fertility both toward their altitudinal and lowland distribution limits, but their fertility optima were different. The performances of the two fern species showed highly different responses to geographical and climatical variables. The fertility of T. limbosperma could be predicted by mean July- and January temperatures, humidity and canopy cover, while the fertility of A. distentifolium could not be predicted by any of the site environmental variables investigated.     

ANATOMICAL STUDIES OF CYATHEA AND TRICHIPTERIS (CYATHEACEAE)

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.