Citrus in West Africa,with special reference to Liberia

Although ample evidence has been gathered to show that citrus can be grown in many parts of West Africa, relatively little of it is cultivated there at present because of difficulties in transportation and communication. Shifting agriculture is still characteristic of the region, and tradition makes the growing of any introduced tree crop difficult.     

Regeneration of Cyperaceae, with particular reference to seed ecology and seed banks

Cyperaceae (sedges) are an important component of many ecosystems. To understand better their regeneration, we examined seed ecology, including dispersal, seed characteristics, and germination behavior that relate to seed bank development and persistence. We also evaluated sedge seed banks from 104 studies, representing a wide array of habitats. Sedge seed bank development and persistence were associated with germination and dormancy traits, namely: dormancy level, seasonal dormancy patterns, and requirement for light, alternating temperatures, and aerobic conditions. Interplay of traits appears to have resulted in low-risk germination strategies adapted to exploit infrequent occurrence of gaps and facilitate formation of persistent seed banks. A variety of dispersal modes and morphological adaptations occurred, but many species had no apparent specialized structures. The main dispersal vectors were water and then animals. About 216 species, in 21 genera, were recorded in the seed bank survey. High densities (>50,000 m⁻²) occurred occasionally in wet habitats, but generally values were low (<500 m⁻² in 70% of entries). Species richness was also generally low (mean 4.8 species study⁻¹), but ranged from 10 to 33 species in certain wetlands. Our studies showed varied reproductive strategies within habitats, persistence, and ability of many species to colonize disturbed habitats. Overall, seed banks tended to be persistent (>1 year). Maximum longevity ranged between 10 and 295 years, but for certain species viability was lost in <3 years. Seeds of many sedges occurred in deeper soil layers to depths >1 m. Seed production, low in rhizomatous species, ranged between 0 and 345,000 seeds m⁻² year⁻¹. Amphicarpy or pseudo-viviparous plantlets occurred in limited numbers of species. The relation between seed production, seed rain, and seed bank is largely obscure and awaits further investigation. For successful restoration and species conservation projects, seed banks (or a source of seeds) are necessary, combined with suitable germination and establishment conditions. Future seed bank studies are considered.     

Aquatic Oligochaeta in Italy, with special reference to Naididae

We present a list of Italian freshwater and marine Oligochaeta in the families Lumbriculidae, Haplotaxidae, Tubificidae, Naididae, Propappidae, Criodrilidae, and Lumbricidae, representing 57 genera and 130 species. Published data reflect the incomplete knowledge of the Italian oligochaete fauna, restricted to certain geographical areas. Subterranean aquatic and marine fauna are of particular interest as these have been studied the least. We provide a comprehensive review of the Naididae including, for the first time, southern Italy and the islands of Sicily and Sardinia. The distribution of species is discussed and taxonomic problems arising from the morphological variability of Italian material are examined.     

Approaches to the identification of angiosperm leaf remains

During the past 125 years the history of early angiosperms, interpreted through the fossil leaf record has been largely an exercise in paleofloristic studies, ignoring evolution. Imprecise identifications of ancient leaves “matched” to extant genera and families have been used as the basis for reconstructions of paleocommunities and paleoclimates. However, as the result of careful morphological studies of leaf form, venation and cuticular features new insights into the evolution of angiosperms are now available. In this paper considerations are given to the usefulness and shortcomings of leaf form, venation and cuticular analysis as diagnostic tools of plant identification. Many techniques for the study of the morphology of modern and fossil leaves are included in this paper as well as tables outlining features of leaf venation and the epidermis. Careful morphological studies of leaf form (such as the venation and epidermal characters emphasized in this paper) will provide better understanding of the relationships of living angiosperms and transform the fossil leaf record into useful data that can be used to study the evolution of the angiosperms.     

Methods of estimating seed banks with reference to long-term seed burial

We compared two standard seed-bank estimation techniques using buried seed populations that had been covered to depths of >1 m by volcanic deposits for 20 years. Some seeds were germinated in a greenhouse (germination method [GM]), and other seeds were extracted by flotation using 50% K₂CO₃ solution (floatation method [FM]). In total, FM could detect more species and seeds in the soils than GM. However, many species that were extracted by FM did not germinate by GM and smaller seeds were extracted to a lesser extent by FM. FM and GM have distinct advantages and disadvantages. We concluded that the application of a single method should be avoided in estimating seed banks, in particular for long-lived seed banks, because the seeds cannot be readily germinated and are structurally weak.     

Plant remains from Sardinia,Italy with notes on barley and grape

This paper presents archaeobotanical results from Sardinia, an island in the western Mediterranean. The starting point is the material excavated at Duos Nuraghes near Borore, but remains provided by other sites are taken into account as well. Naked wheat, presumably a tetraploid wheat such as Triticum durum Desf. (macaroni wheat), and Hordeum vulgare L. (barley) are the most common finds from the Neolithic up to the Medieval period. Triticum dicoccum Schübl. (emmer), Lens culinaris Medik. (lentil), Pisum sativum L. (pea) and Vicia faba L. var. minor (horse bean) have been grown as well. A medieval context revealed Beta vulgaris L. (beet). The most common find in the category of fruits is Vitis vinifera L. (grape). The overall picture is one of continuity in agricultural practices. Nevertheless this picture may be false. In the early Bronze Age the cultivation of barley may have shifted from the naked variety towards the hulled variety. The Phoenicians may have introduced new cultivars of grapevine, although the native grapevine was not replaced by these. The weed taxa suggest some change in agriculture from Punic or Roman times onwards. Received August 10, 2001 / Accepted January 15, 2002     

Sexual differences in European Neanderthal crania with special reference to the Krapina remains

Problems relating to the identification of sex in Neanderthal specimens are discussed. Three morphological features—morphology of the mastoid process and surrounding area, form of the supraorbital torus at glabella and the superciliary region, and the rugosity of the nuchal plane—were selected as most indicative of sex in Neanderthal crania based on observations from the Krapina collection and on those European specimens with pelvicly determined sex. Thirteen Neanderthal crania (eight males, five females) are sexed on the basis of these criteria, and the pattern and degree of sexual dimorphism determined for this sample is compared to those exhibited by other samples of more recent European hominids. It is concluded that the degree of sexual dimorphism in Neanderthal crania, as defined by this study, is consistent with that observed in the other fossil samples and that Neanderthals exhibit slightly more cranial sexual dimorphism than more recent Europeans. Models for explaining this are discussed as is the difference in pattern of change and degree of sexual dimorphism between the cranium and postcranium during later prehistoric hominid evolution in Europe.     

The solution of goose damage problems in The Netherlands, with special reference to compensation schemes

In The Netherlands farmers can apply to the Game Fund in order to receive compensatory payments in the event of damage by wild mammals and birds. In recent years the amount of money paid annually has increased up to £758,000. Although adequate as a basic measure to offset the losses suffered, the large increase in the total amount involved leads to questions about the accuracy of the estimated damage in relation to the actual crop reduction.
In certain areas in The Netherlands research is aimed at minimizing damage by altering land use in agricultural areas and restoring original habitats for wintering geese. This is a new approach for solving the apparent future conflict between a further increase of the amount of money paid to refund the damage claimed and the aims of conservation.     

Structure and development of the ovule and seed in Aristolochiaceae, with particular reference to Saruma

All members of Aristolochiaceae have anatropous, bitegmic, crassinucellate ovules, which are endostomic except in Saruma and Asarum arifolium where ovules are amphistomic. The outer integument is two cell-layered and the inner integument is three cell-layered. The chalazal megaspore is the functional one. All these conditions appear to be plesiomorphic for the order Piperales, which consists of five families, Aristolochiaceae, Hydnoraceae, Lactoridaceae, Piperaceae and Saururaceae. The embryo sac in Aristolochiaceae is eight-nucleate and corresponds to the Polygonum type; a hypostase is frequently present in this family. The seed coat of Aristolochia s.l., Asarum, Saruma and some Thottea species consists primarily of a two cell-layered testa, and a three cell-layered tegmen. In some species the cells of the outer epidermis become radially elongated, forming reticulate wall thickenings. Cells of the inner layer of the testa have crystals and thickened inner walls. The three layers of the tegmen are tangentially elongated, and become cross fibres at maturity, as fibres of the outer and inner layers are parallel to the seed axis, whereas those of the middle layer are perpendicular to it. This type of seed coat anatomy is synapomorphic for Aristolochiaceae. In addition, the gross morphology of the seed and elaiosome histology are remarkably similar in Asarum and Saruma, thus supporting a sister-group relationship between them. Embryological and seed characters do not supply any synapomorphy that support a close relationship between Aristolochiaceae, Hydnoraceae and Lactoridaceae. Instead, some seed features such as the absence of seed appendages and the collapsed cells of endotesta may indicate a close relationship of Lactoris with Piperaceae plus Saururaceae, although this is the subject of further analysis.     

An inventory of British remains of Homotherium (Mammalia,Carnivora, Felidae), with special reference to the material from Kent's Cavern

The genus Homotherium, while wide ranging in Eurasia, has only been considered a sporadic component of the British Pleistocene fauna. The Early Pleistocene Homotherium crenatidens and the Middle to Late Pleistocene Homotherium latidens have however held a prominent position in the annals of the 19th century British geology and the discussion of the antiquity of man. As many of the UK sites containing Homotherium were first investigated over a hundred years ago, the literature is quite confused on the question of what was found and where it was finally curated. An attempt has been made to track down all specimens of British Homotherium mentioned in the literature and to give their current location. As part of this study, I correctly identify for the first time all the Homotherium canines from Kent's Cavern pictured in the famous Plate F of MacEnery. Additionally, a single Homotherium incisor, found by MacEnery, is deduced from the study of his surviving writings and images.     

Emergence and Phylodynamics of Citrus tristeza virus in Sicily,Italy

Citrus tristeza virus (CTV) outbreaks were detected in Sicily island, Italy for the first time in 2002. To gain insight into the evolutionary forces driving the emergence and phylogeography of these CTV populations, we determined and analyzed the nucleotide sequences of the p20 gene from 108 CTV isolates collected from 2002 to 2009. Bayesian phylogenetic analysis revealed that mild and severe CTV isolates belonging to five different clades (lineages) were introduced in Sicily in 2002. Phylogeographic analysis showed that four lineages co-circulated in the main citrus growing area located in Eastern Sicily. However, only one lineage (composed of mild isolates) spread to distant areas of Sicily and was detected after 2007. No correlation was found between genetic variation and citrus host, indicating that citrus cultivars did not exert differential selective pressures on the virus. The genetic variation of CTV was not structured according to geographical location or sampling time, likely due to the multiple introduction events and a complex migration pattern with intense co- and re-circulation of different lineages in the same area. The phylogenetic structure, statistical tests of neutrality and comparison of synonymous and nonsynonymous substitution rates suggest that weak negative selection and genetic drift following a rapid expansion may be the main causes of the CTV variability observed today in Sicily. Nonetheless, three adjacent amino acids at the p20 N-terminal region were found to be under positive selection, likely resulting from adaptation events.     

The identification of growth stages in winter wheat with reference to the application of growth-regulator herbicides

The development of several varieties of winter wheat {Triticum aestivum) in early spring was studied in order to relate the progress of apical differentiation to easily measured external characters and so provide a guide to the correct timing of herbicide applications. Leaf sheath lengths were more closely related to apical development than were tiller or leaf numbers. Spikelet differentiation occurred when the longest sheaths were c. 5 cm tall. Application of a growth regulator herbicide before this stage of development caused ear deformities in the crop at harvest. A measure of leaf sheath length might, therefore, replace the ambiguous criteria presently used to judge the stages of winter wheat most tolerant of herbicides.     

The cell types in the adenohypophysis of the South-American lungfish,Lepidosiren paradoxa,with special reference to immunocytochemical identification of the corticotropin-containing cells

The histological features and distribution of cell types in the distal lobe of Lepidosiren resemble those of Protopterus. Three "basophilic" cell types are described, whereas the identification of two acidophilic cell types is uncertain. In the intermediate lobe two cell types have been found. Anti-(1-24)ACTH IgG was used in the unlabeled antibody-enzyme method to identify corticotropin-containing cells in the adenohypophysis of Lepidosiren with light and electron microscopy. Corticotropin was demonstrated in cells of the distal lobe and the intermediate lobe. The staining reaction in the distal lobe is localized in the rostrally distributed lead-hematoxylin positive cells. At the ultrastructural level the immunoreaction in these distal lobe cells is localized on polymorphic granules ranging from 130 to 210 nm. Absorption experiments show that the immunoreactive cells in the distal lobe contain at least residues 1-3 and 14-17 of the naturally occurring corticotropin hormone, while the intermediate lobe cells contain alpha-MSH or at least residues 1-3 of ACTH. The plasma level of corticotropin was determined to be 71 ng/l by means of radioimmunoassay (RIA).     

Mitoses in thermodormant lettuce seeds with reference to histological location,localized expansion,and seed storage

Summary Seeds from one lot of New York lettuce were sown in each of 5 successive years to compare the effect of duration of storage on the capacity for mitosis in thermodormant seeds with the effect of storage on the capacity for germination under conditions favorable for germination. Whereas the capacity for mitosis in absence of germination increased as a function of duration of seed storage, the capacity for germination itself decreased steadily over the period studied. Thus, the apparent deterioration of stored seed, as measured by decreased germination, does not necessarily indicate a general deterioration of all cytologic processes. Histological study of thermodormant lettuce seeds demonstrated that in some seeds mitosis and cytokinesis can occur without either overall or localized expansion of the embryo-axis. Although localized expansion occurred in some seeds, there was no expansion of the embryo-axis as a whole in any of the seeds, the localized expansion being accompanied always by localized compression elsewhere in the axis. Restraint of the embryo by the endosperm, which remained intact, could account for the prevention of overall expansion of those embryos in which localized expansion and compression occurred. Mitoses in such embryos occurred both within and outside the regions of localized expansion. Thus, even in those embryos with localized expansion, mitotic activity is not necessarily correlated with expansion. Mitoses occurred in each of the primary tissue meristems of the hypocotyl-radicle, mainly within the apical 0.5 mm of the radicle. In this regard, thermodormant embryos resemble growing roots of lettuce seedlings. These findings demonstrate that mitotic activity and localized expansion, either separately or together, can occur in the embryo without germination.Research sponsored by the U.S. Atomic Energy Commission under contract with the Union Carbide Corporation.The authors are grateful to Miss Sarah A. Angel and Mrs. Helen J. Luippold for their technical contributions to this work.     

Ecological aspects of the introduction of fish species into natural habitats in Europe, with special reference to the Netherlands

A total of 39 fish species has been introduced into European waters, mainly during the 19th and 20th centuries: 20 European species (12 successful), 3 Asian species (1 successful), 16 North American species (13 successful). Several successful introductions have produced unexpected and detrimental side-effects; especially introductions of piscivorous species have created problems. Introductions of the latter type of fishes should be most carefully considered. The aim of fish introductions should preferably be to create temporary populations of non-reproducing fishes whose numbers can be completely controlled by man.