Barley, like most other grasses that have been studied, contains two kinds of sieve tube. The first formed are called thinwalled sieve tubes because of their thin wall compared to the late-formed, and are associated with companion cells. The late-formed are thick-walled sieve tubes, which differentiate next to the metaxylem vessels and lack companion cells. Aphid (Sitobion yakini (Eastop) feeding was studied using light microscopy to determine if they preferentially feed from thin- or thick-walled sieve tubes in the barley leaf. Penetration of the stylets through the leaf epidermis and mesophyll was largely intercellular, becoming partly intercellular and, partly, intracellular inside the vascular bundle. Sixteen of 19 pairs of stylets (84%), and 293 of 317 (92%) stylet tracks terminated at the thin-walled sieve tubes, suggesting that Sitobion yakini feeds preferentially on the thin-walled sieve tubes which seem to be more attractive to the aphid. These thin-walled sieve tubes are thus probably the most functional in terms of phloem loading and transport.

There is considerable pressure on conservation planners to use existing data from herbarium and museum collections for planning and monitoring, despite the weaknesses of such data. It is thus important to be able to assess the quality of this information. One application of these data is the production of species richness maps. However, sampling effort is generally not consistent throughout a region for maps generated from collections data, and it is thus desirable to identify geographic grid cells (such as quarter degree squares: QDS) for which there has been low sampling effort. We describe a technique that can be used to identify QDS that are likely to have low species richness that is due to insufficient sampling effort rather than to low actual species richness. The technique exploits relationships between climate and species richness to detect QDS that are poorly sampled. This approach offers advantages over the current practice of applying a single threshold across the entire map region to detectQDSthat are poorly sampled. Here we report on the application of our technique to plant species richness data in the PRECIS database. Results reveal that the majority of QDS in the Flora of Southern Africa region can be considered to be poorly sampled, even when using conservative thresholds for richness values. The advantages and weaknesses of the technique are discussed and issues requiring further investigation are highlighted.

No description available.

[From the introduction]: Horses played a major role in the transport system in Britain until, in the years following the conclusion of the First World War, they were gradually ousted by motor vehicles. In 1917, when the first reasonably complete equine census of Britain was undertaken, there were 2,650,773 horses in the country, 1,115,920 of which were used for agricultural purposes (Chivers, 1976). Horse breeding was therefore of great importance and a variety of attempts was made to improve the quality of horses by subsidising stallions that travelled the countryside during the breeding season, and that were available, at a fee, for the service of mares. This paper describes some of the routes followed by stallions that formerly travelled in Brycheiniog and adjacent counties.

Prior to the current constitutional dispensation, the development of South African administrative law was restricted by the doctrine of Parliamentary Sovereignty. Even in that comparatively 'hostile' environment, review for unreasonableness developed as an aspect of judicial review, and was applied as a check on the exercise of administrative power in certain circumstances. The principle of proportionality as an aspect of review for unreasonableness also developed during this period. With the advent of the new Constitutional dispensation, the framework within which administrative law in South Africa operates became one governed by Constitutional Supremacy. The Rights to Just Administrative Action, including a right to reasonable administrative action, were entrenched in the Constitution. Review for unreasonableness is an important aspect of administrative law in the present Constitutional dispensation as the mechanism for protecting the Constitutional right to reasonable administrative action. Proportionality is an important principle underlying the Bill of Rights as a whole, and it is an important aspect of the right to reasonable administrative action, and of review for unreasonableness. In early 2000, the Promotion of Administrative Justice Act No. 3 of 2000 ("the PAJA"), was passed by Parliament in fulfillment of the Constitutional requirement to pass legislation to give effect to the constitutional rights to Just Administrative Action. This thesis examines whether or not review for unreasonableness, and proportionality as an aspect of review for unreasonableness, have been meaningfully incorporated in the PAJA, and if they have not been, what potential remedies there might be. This is done by examining the basis of judicial review both before and under the current constitutional dispensation; defining unreasonableness, and proportionality; examining the content of the right to administrative action which is "justifiable in relation to the reasons given" in section 24(d) of the Interim Constitution and the right to reasonable administrative action in terms of section 33(1) of the Final Constitution; examining the application of review for unreasonableness and proportionality by the Courts both before and under the current constitutional dispensation; examining the content of judicial review incorporated in the PAJA and the drafting history of section 6(2) of the PAJA which relates to review for unreasonableness; drawing conclusions regarding whether or not review for unreasonableness and proportionality were meaningfully incorporated in the PAJA; and finally making recommendations with regard to review for unreasonableness and proportionality in light of the provisions of the PAJA.

We have used transmission electron microscopy to examine plasmodesmata of the charophycean green alga Chara zeylanica, and of the putatively early divergent bryophytes Monoclea gottschei (liverwort), Notothylas orbicularis (hornwort), and Sphagnum fimbriatum (moss), in an attempt to learn when seed plant plasmodesmata may have originated. The three bryophytes examined have desmotubules. In addition, Monoclea was found to have branched plasmodesmata, and plasmodesmata of Sphagnum displayed densely staining regions around the neck region, as well as ring-like wall specializations. In Chara, longitudinal sections revealed endoplasmic reticulum (ER) that sometimes appeared to be associated with plasmodesmata, but this was rare, despite abundant ER at the cell periphery. Across all three fixation methods, cross-sectional views showed an internal central structure, which in some cases appeared to be connected to the plasma membrane via spoke-like structures. Plasmodesmata were present even in the incompletely formed reticulum of forming cell plates, from which we conclude that primary plasmodesmata are formed at cytokinesis in Chara zeylanica. Based on these results it appears that plasmodesmata of Chara may be less specialized than those of seed plants, and that complex plasmodesmata probably evolved in the ancestor of land plants before extant lineages of bryophytes diverged.

The prevalence of use and commercial value of wild edible herbs in South Africa is examined from four recent quantitative studies at eight different sites. The use of wild edible herbs was widespread in rural communities, with over 90% of households using them in all but one sample site. Mean frequency of use in season was generally between two and five times per week, with a mean of four times across all sites. But many households consume them daily. Use in winter was less than in summer. The mass of wild edible herbs consumed ranged from 12 kg to over 130 kg per household per year. Local (farm-gate) prices ranged from R2.65 to R72 per kilogram, but were generally between R30 and R40 per kg. Direct-use value to consuming households ranged from R85 to almost R5000 across the eight sites, with a mean of R1020 per user household per year. Although harvesting of wild herbs takes time, the high gross direct-use value represents a considerable saving on having to purchase commercial alternatives. Key species differ from place to place both in availability and use, and include both indigenous and exotic species. Commonly used genera include Amaranthus, Bidens, Chenopodium, Cleome, Corchorus, and Momordica. The use, value and trade in wild edible herbs currently receives no recognition in land and agrarian reform policies. It is imperative that this be addressed, and the relationships between rural livelihoods, use of wild edible herbs, food security, and land and resource tenure be clarified, and debated within the policy forums around different models for, and delivery of, agrarian reform and rural development.

Multivariate discriminant analyses of nine standard morphometric characters of honeybee workers were used to track the origin of a social parasitic pseudo-clone of thelytokous laying workers that have invaded colonies of Apis mellifera scutellata in South Africa. Twenty social parasitic workers were sampled from both of two infested A. m. scutellata colonies at two distant apiaries (Graskop and Heilbronn, about 390 km apart) and compared with data obtained from 80 colonies in four different geographical zones (zone I: thelytokous A. m. capensis morphocluster; zone II: natural thelytokous hybrids between A. m. capensis and A. m. scutellata; zone III: thelytokous A. m. scutellata morphocluster; zone IV: an arrhenotokous A. m. scutellata morphocluster). Thelytokous laying workers occur naturally in zones I-III. Highly significant morphometric differences were found among the bees in the four zones. The data support the conclusion that the social parasitic workers belong to the thelytokous A. m. capensis morphocluster. It is most likely that the social parasitic workers originated from the heart of the Cape bee's distribution range in the Western Cape region in zone I. Morphometric analysis makes it feasible to restrict the possible origin of the social parasitic workers from the natural distribution range of thelytoky (approximately 240 000 km2) down to about 12 000 km2, which represents a resolution capacity of about 95%.

Human-induced fires are a major disturbance in Baikiaea plurijuga woodland savannas that are economically important for timber production. Most fires occur during the late dry season, when they may severely damage woody plants. Prescribed burning during the early dry season is a management strategy to reduce fuel loads and thus the incidence of intense fires during the late dry season. There is, however, little information on fire behaviour characteristics of early dry season fires.We studied the relationship between experimental fuel conditions and fire behaviour by lighting 15 fires during the early dry season in a Baikiaea woodland. Fire intensity ranged from 25 to 1341 kW m[superscript (-1)], while rate of spread of fire varied between 0.01 and 0.35ms[superscript (-1)]. Fire intensity and rate of spread were positively related to flame height, leaf-scorch height and proportion of the area burnt. The relationships suggest that fire characteristics can be retrospectively determined using a variable such as scorch height. The grass fuel load, wind speed, relative humidity and to a lesser extent fuel moisture were important predictors of rate of spread, flame height, leaf-scorch height and proportion of the area burnt, with no impact due to the litter fuel load. The grass fuel load and wind speed had a positive effect on rate of spread, whereas relative humidity and fuel moisture had a negative effect. These findings indicate that managers can predict the likely damage to woody plants during an early dry season burn by assessing the grass fuel load and weather conditions at the time of burning.

Entomological forensic evidence has been used in southern Africa for decades but explicitly forensic research began in southern Africa only 26 years ago. Although applicable local research has accumulated since 1921, it is scattered in a diverse literature or unpublished. Some overseas research has also touched on local species. This review uses a historical approach to synthesize the southern African literature and to illustrate the cross-disciplinary, opportunistic nature of forensic entomology. Distinct phases of research focused on agriculture (1921-1950), medicine (1952- 1965), ecology (1968-1990) and forensics (1980-2005), but systematics spanned the entire period and tended to be ad hoc. Few scientists were involved, situated at geographically distant locations and with widely disparate research interests. The review concludes with an overview of southern African entomologists who have been involved in medico-legal investigations, and a critical evaluation of the past and future of the discipline locally.