A new species of the marattialean fern Scolecopteris (Zenker) Millay from the uppermost Permian of Guizhou Province, south-western China

Several isolated marattialean synangia and sporangia are reported from coal balls collected from Coal Seam No.1 (C605) in the uppermost Permian Wangjiazhai Formation in Guizhou Province, south-western China. The synangia are radially symmetrical with diameters between 0.8 and 1.2 mm and are 1.7 mm long, consisting of 3–4 elongate sporangia that are fused basally, free distally and possess a pointed apex. The outer-facing sporangial wall is 4–5 cells thick and conspicuously differentiated. Spores are trilete, have a granular ornamentation and are nearly round equatorially with a diameter of 55–60 µm. Comparisons with other anatomically preserved Palaeozoic marattialean synangia from the Euramerican and Cathaysian floras permit their assignment to the genus of Scolecopteris (Zenker) Millay. In this species the thick, outer-facing sporangial walls and large trilete spores are features consistent with those of the Oliveri Group within Scolecopteris , a group that has previously been considered primitive within this genus. Distinctions from all other previously recognized species within the Oliveri Group lead to the creation of a new species, S. guizhouensis sp. nov. This species is the youngest of the reported species of Scolecopteris recognized from the Euramerican and Cathaysian floras, and provides important evidence on the organization of marattialean ferns from the Upper Permian strata of south China.  © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society , 2006, 151 , 279–288.     

Xylem heterochrony: an unappreciated key to angiosperm origin and diversifications

All angiosperms can be arranged along a spectrum from a preponderance of juvenile traits (cambial activity lost) to one of nearly all adult characters (cambium maximally active, mature patterns realized rapidly early in ontogeny). Angiosperms are unique among seed plants in the width of this spectrum. Xylem patterns are considered here to be indicative of contemporary function, not relictual. Nevertheless, most families of early‐divergent angiosperms exhibit paedomorphic xylem structure, a circumstance that is most plausibly explained by the concept that early angiosperms had sympodial growth forms featuring limited accumulation of secondary xylem. Sympodial habits have been retained in various ways not only in early‐divergent angiosperms, but also among eudicots in Ranunculales. The early angiosperm vessel, relatively marginal in conductive abilities, was improved in various ways, with concurrent redesign of parenchyma and fibre systems to enhance conductive, storage and mechanical capabilities. Flexibility in degree of cambial activity and kinds of juvenile/adult expressions has been basic to diversification in eudicots as a whole. Sympodial growth that lacks cambium, such as in monocots, provides advantages by various features, such as organographic compartmentalization of tracheid and vessel types. Woody monopodial eudicots were able to diversify as a result of production of new solutions to embolism prevention and conductive efficiency, particularly in vessel design, but also in parenchyma histology. Criteria for paedomorphosis in wood include slow decrease in length of fusiform cambial initials, predominance of procumbent ray cells and lesser degrees of cambial activity. Retention of ancestral features in primary xylem (the ‘refugium’ effect) is, in effect, a sort of inverse evidence of acceleration of adult patterns in later formed xylem. Xylem heterochrony is analysed not only for all key groups of angiosperms (including monocots), but also for different growth forms, such as lianas, annuals, various types of perennials, rosette trees and stem succulents. Xylary phenomena that potentially could be confused with heterochrony are discussed. Heterochronous xylem features seem at least as important as other often cited factors (pollination biology) because various degrees of paedomorphic xylem are found in so many growth forms that relate in xylary terms to ecological sites. Xylem heterochrony can probably be accessed during evolution by relatively simple gene changes in a wide range of angiosperms and thus represents a current as well as a past source of variation upon which diversification was based. Results discussed here are compatible with both current molecular‐based phylogenetic analyses and all recent physiological work on conduction in xylem and thus represent an integration of these fields. © 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 161 , 26–65.     

Do tracheid microstructure and the presence of minute crystals link Nymphaeaceae,Cabombaceae and Hydatellaceae?

Original scanning electron microscopy (SEM) observations are presented for stems of Brasenia schreberi and Cabomba caroliniana of Cabombaceae and three species of Trithuria of Hydatellaceae. End walls of stem tracheids of Brasenia have the same peculiar microstructure that we have reported in Barclaya, Euryale, Nuphar, Nymphaea (including Ondinea) and Victoria of Nymphaeaceae. This feature unites Cabombaceae with Nymphaeaceae. The minute rhomboidal crystals on the surfaces of stellate parenchyma cells of Brasenia reported by Solereder (1906. Oxford: University Press), but not noticed since, are figured. They are like the minute crystals of the often‐mentioned astrosclereids of Nymphaeaceae. Neither of these two features has been observed in Hydatellaceae. If the absence of these two features can be confirmed, the reason may be more related to ecology, development, habit and anatomical organization than to degree of phylogenetic relationship as shown by molecular studies. Anatomical observations on the stem anatomy of Trithuria are offered on the basis of paraffin sections prepared for a paper by Cheadle & Kosakai (1975. American Journal of Botany 62: 1017–1026); that study is notable for a discrepancy between an illustration of a specialized vessel element on the one hand and tabular data indicating long scalariform perforation plates on the other. Long scalariform perforation plates are mostly found in scalariformly pitted vessels of monocots, whereas the tracheary elements of Trithuria mostly have helical or annular thickenings. We were unable to demonstrate the presence of vessels in Hydatellaceae. © 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 159 , 572–582.     

Some new Darwin vascular plant specimens from the Beagle voyage

This paper reports 24 newly discovered specimens of 21 species made by Charles Darwin in Argentina, Australia, Brazil, Chile, Ecuador and Uruguay while on the 1831–1836 voyage of HMS Beagle. They have been found in Cambridge University Herbarium and the herbaria of the Missouri Botanical Garden, Natural History Museum, London, New York Botanical Garden and the Royal Botanic Gardens, Kew, since the earlier publications of Porter. Included are type specimens of Calceolaria darwinii (isotype; = C. uniflora), Cuscuta gymnocarpa (holotype and isotypes), C. sandwichiana var. mimosae (isolectotypes = C. gymnocarpa), Ephedra frustillata (lectotype and isolectotypes), Ourisia breviflora (isolectotype), Polypodium paleaceum (syntype?; = Ctenitis sloanei) and Urera gaudichaudiana (holotype; = Laportea aestuans). © 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 159 , 12–18.     

A summary of fossil records for Arecaceae

Of all monocotyledons the Arecaceae displays by far the richest fossil record, and there is an extensive literature. The earliest unequivocal fossil palm material probably dates from the early to mid Late Cretaceous (Turonian > Coniacian > Santonian). The records are geographically widespread and comprise a wide range of organs: leaves, cuticles, stems, rhizomes, roots, fruits, seeds, endocarps, rachillae, peduncles, inflorescences, individual flowers and pollen. For some of these organs records are rare while for others, such as leaves, stems and pollen, records are abundant. However, fossil material often lacks sufficient diagnostic detail to allow reasonable association with living palm taxa beyond, or even to, subfamilial level. Nevertheless, many fossil genera and numerous species have been described. A brief survey of palm fossil records is presented, and their taxonomy and morphological limitations are considered. © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society , 2006, 151 , 39–67.     

Comparative floral structure and systematics in Crossosomatales (Crossosomataceae, Stachyuraceae, Staphyleaceae, Aphloiaceae, Geissolomataceae, Ixerbaceae, Strasburgeriaceae)

Floral structure of all putative families of Crossosomatales as suggested by molecular studies was comparatively studied. The seven comprise Crossosomataceae, Stachyuraceae, Staphyleaceae, Aphloiaceae, Geissolomataceae, Ixerbaceae, and Strasburgeriaceae. The entire clade (1) is highly supported by floral structure, also the clades (in sequence of diminishing structural support): Ixerbaceae/Strasburgeriaceae (2), Geissolomataceae/Ixerbaceae/Strasburgeriaceae (3), Aphloiaceae/Geissolomataceae/Ixerbaceae/Strasburgeriaceae (4), and Crossosomataceae/Stachyuraceae/Staphyleaceae (5). Among the prominent floral features of Crossosomatales (1) are solitary flowers, presence of a floral cup, imbricate sepals with outermost smaller than inner, pollen grains with horizontally extended endoapertures, shortly stalked gynoecium, postgenitally united carpel tips forming a compitum, stigmatic papillae two‐ or more‐cellular, ovary locules tapering upwards, long integuments forming zigzag micropyles, cell clusters with bundles of long yellow crystals, mucilage cells, seeds with smooth, sclerified testa and without a differentiated tegmen. Clade (2) is characterized by large flowers, petals forming a tight, pointed cone in bud, stamens with long, stout filaments and sagittate anthers, streamlined, conical gynoecium, antitropous ovules, rudimentary aril, lignified, unicellular, T‐shaped hairs and idioblasts with striate mucilaginous cell walls. Clade (3) is characterized by alternisepalous carpels, punctiform stigma formed by postgenitally united and twisted carpel tips, synascidiate ovary, only one or two pendant ovules per carpel, nectary recesses between androecium and gynoecium. Clade (4) is characterized by pronounced ‘pollen buds’. Clade (5) is characterized by polygamous or functionally unisexual flowers, x‐shaped anthers, free and follicular carpels (not in Stachyuraceae). Crossosomataceae and Aphloiaceae, although not retrieved as a clade in molecular studies, share several special floral features: polystemonous androecium; basifixed anthers without a connective protrusion; stigma with two more or less decurrent crests; camplyotropous ovules and reniform seeds; simple, disc‐shaped nectaries and absence of hairs. © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society, 2005, 147 , 1–46.     

Comparative floral structure and systematics in Celastrales (Celastraceae, Parnassiaceae, Lepidobotryaceae)

Floral morphology, anatomy and histology in the newly circumscribed order Celastrales, comprising Celastraceae, Parnassiaceae and Lepidobotryaceae are studied comparatively. Several genera of Celastraceae and Lepidobotrys (Lepidobotryaceae) were studied for the first time in this respect. Celastraceae are well supported as a group by floral structure (including genera that were in separate families in earlier classifications); they have dorsally bulged‐up locules (and thus apical septa) and contain oxalate druses in their floral tissues. The group of Celastraceae and Parnassiaceae is also well supported. They share completely syncarpous gynoecia with commissural stigmatic lobes (and strong concomitant development of the commissural vascular bundles but weak median carpel bundles), only weakly crassinucellar or incompletely tenuinucellar ovules with an endothelium, partly fringed sepals and petals, protandry in bisexual flowers combined with herkogamy by the movement of stamens and anther abscission, and stamens fused with the ovary. In contrast, Lepidobotryaceae are more distant from the other two families, sharing only a handful of features with Celastraceae (not Parnassiaceae), such as pseudohermaphroditic flowers, united stamen bases forming a collar around the gynoecium and seeds with a conspicuous aril. However, all three families together are also somewhat supported as a group and share petals that are not retarded in late floral bud development, 3‐carpellate gynoecia, ventral slits of carpels closed by long interlocking epidermal cells and pollen tube transmitting tissue encompassing several cell layers, both integuments usually more than two cell layers thick, and only weak or lacking floral indumentum. In some molecular analyses Celastrales form an unsupported clade with Malpighiales and Oxalidales. This association is supported by floral structure, especially between Celastrales and Malpighiales. Among Celastrales, Lepidobotryaceae especially share special features with Malpighiales, including a diplostemonous androecium with ten fertile stamens, epitropous ovules with an obturator and strong vascularization around the chalaza. © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society, 2005, 149 , 129–194.     

Khaosokia caricoides, a new genus and species of Cyperaceae from Thailand

Khaosokia caricoides , D.A. Simpson, Chayam. & J. Parn., a newly discovered genus and species of Cyperaceae is described and illustrated. The genus is characterized by a narrowly paniculate dioecious inflorescence with 2–4 nodes, each of the nodes having a leaf-like inflorescence bract that exceeds the inflorescence. Spikelets in both sexes are linear-cylindric and each flower has seven perianth bristles. The nutlet was immature in the specimens examined. The photosynthetic pathway is C₃. Khaosokia is endemic to limestone cliffs in peninsular Thailand; its conservation status is assessed as Vulnerable (VU B1a + 2a). It has affinities to tribes Cariceae, Dulichieae and some members of Scirpeae, but the exact nature of these relationships has yet to be determined. A revised key to the genera of Cyperaceae in Thailand is presented.  © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society , 2005, 149 , 357–364.     

Pollen morphology of the tribes Naucleeae and Hymenodictyeae (Rubiaceae – Cinchonoideae) and its phylogenetic significance

The tribe Naucleeae has recently been recircumscribed on the basis of both morphological and molecular [ rbcL , trnT-F , internal transcribed spacer (ITS)] evidence, and has been found to be the sister group of the tribe Hymenodictyeae Razafim. & B. Bremer. In order to find pollen morphological support for this new classification, the pollen and orbicules of 65 species, representing 23 Naucleeae and the two Hymenodictyeae genera, were investigated by scanning electron and light microscopy. Naucleeae pollen is very small (< 20 µm) to small (20–30 µm) and its shape in equatorial view is suboblate to spheroidal or, more rarely, subprolate. Three compound apertures are present, each comprising a long and narrow ectocolpus, a circular to slightly lolongate mesoporus, and an often H-shaped endoaperture. The sexine ornamentation is perforate, rugulate, or (micro)reticulate, and supratectal elements are always absent. Apart from the variation in sexine ornamentation, the tribe is rather stenopalynous. The pollen of Hymenodictyeae is very similar to that of Naucleeae. The H-shaped endoapertures often observed probably form a synapomorphy for the clade comprising Naucleeae and Hymenodictyeae. Our pollen morphological observations are not in conflict with the widened delimitation of Naucleeae. Unambiguous pollen support for the recent subtribal or generic concepts of Naucleeae could not be found because of a lack of variation of pollen characters within the tribe. Orbicules are invariably present in the ten Naucleeae taxa investigated. They are spheroidal and smooth or irregularly folded.  © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society , 2007, 153 , 329–341.