A new species of Rhus (Anacardiaceae), endemic to serpentine near Barberton, Mpumalanga (Eastern Transvaal), South Africa

Rhus pygmaea , a new species endemic to amphibolitic serpentine soils near Barberton, Mpumalanga (Eastern Transvaal) is described and illustrated. It has affinities with R. pondoensis Schonl., but differs primarily in its dwarf habit, narrower leaflets, reduced inflorescence and male flowers having a conical pistillode.     

Remains of secretory cavities in pinnules of Stephanian pteridosperms from Blanzy-Montceau (Central France): a comparative study

Remains of secretory cavities, so-called resin or secretion bodies, in pinnules of Stephanian pteridosperms from the Blanzy-Montceau Basin (Central France) are examined from cuticles of four species: Dicksonites leptophylla, D. pluckenetii, Pseudomanopteris paleaui , and P. ribeyronii . The distribution of the secretion bodies in pinnules may be (1) simple and in consistent patterns, (2) random, but topographically unequal, or (3) completely random. Differences in the morphology of the bodies may be related to different modes of development of the secretory cavities, i.e. schizogenous or (schizo-) lysigenous development. The value of using these features in fossil plant taxonomy is discussed. Finally, some comments on possible ecological functions of the secretion of lipophilic substances in pteridosperm pinnules are suggested. The secretion of lipophilic substances is abundant among taxa with a vine-like life-form, and this may be related to special demands on protection of climbing or scrambling plants.     

An evaluation of standard oak tree growth in Ruislip woods, West London

Tree-ring studies on dominant and co-dominant oak standards from four woodlands on the western fringes of London were studied in relation to known historical and meteorological conditions. Whilst previous studies suggested a decline in oak growth in recent decades, this was not apparent from this study. Major recruitment periods for the large oaks were determined. The sites had differing responses to known drought years. Coppicing of the undergrowth was found not to greatly influence the growth of the remaining standard trees on all occasions, although one woodland showed some growth release following recent coppicing. Records of lichens for each woodland were used to assess changing pollution levels at the sites.     

Systematic and comparative anatomy of Cymbidieae (Orchidaceae)

Cymbideae comprise an assemblage of 28 genera nearly all of which are represented in this study. Their anatomy is relatively homogenous with the exception of Govenia , in which roots lack velamen and pseudobulb vascular bundles lack sclerenchyma, conditions that do not obtain in other genera. Marginal fibre bundles in leaves of Grammatophyllum and Porphyroglottis consist of clusters of thicker-walled, narrower, epidermis-facing fibres as well as thinner-walled, wider, mesophyll-facing fibres. This feature also occurs in some species of Maxillaria . Baculate tilosomes appear in the roots of a majority of genera in Cymbidieae, as they do in species of Maxillaria , confirming DNA analyses showing a close relationship between tribes Cymbidieae and Maxillarieae. Govenia is singled out both on anatomical and molecular grounds as being ill-placed in Cymbidieae. Cladistic analysis produces only a few tentative hypotheses of phylogenetic relationships among the 28 genera, showing that anatomical characters are of limited value in assessing affinities within this tribe. © 2002 The Linnean Society of London, Botanical Journal of the Linnean Society , 2002, 139 , 1–27.     

Acclimation or stress symptom? An integrated study of intraspecific variation in the clonal plant Aechmea bromeliifolia,a widespread CAM tank‐bromeliad

The clonal tank-bromeliad Aechmea bromeliifolia (Rudge) Baker was found in four different habitats in a restinga (vegetation mosaic on sandy coastal plains), of south-eastern Brazil. These habitats (swamp forest, dry forest, dry shrubland and herbaceous marsh) lie within a few hundred metres of each other along a gradient extending inland from the coast, and differ markedly in terms of light and flood regime. We compared ramet morphology, leaf anatomy and physiology, and population parameters to examine the amplitude of trait variation of this widespread species in the studied restinga. This integrated approach allowed us to examine which variation conferred acclimation and which was merely a stress symptom. A . bromeliifolia showed site-specific differences in abundance, distribution, rosette size and shape, leaf anatomical arrangement and photochemical efficiency (potential quantum yield; F _v/ F _m) during the day. Most of the variation found seemed to be related to the interaction of light and flooding. The lowest number and size of ramets at the exposed, dry shrubland was matched by a marked leaf photoinhibition, which suggested poor acclimation to local levels of light intensity and limited water supply. In the other habitats, the morpho-physiological parameters measured suggested adequate foraging behaviour and site acclimation.  © 2002 The Linnean Society of London, Botanical Journal of the Linnean Society, 2002, 140 , 391-401.