Pollen morphology of the dichapetalaceae with special reference to evolutionary trends and mutual relationships of pollen types

Pollen grains of all three genera of Dichapetalaceae (Dichapetalum, Stephanopodium and Tapura) comprising about 150 species have been studied. Twenty-nine pollen types were recognized and the family has to be considered eurypalynous. A key to the pollen types is added. Based on evolutionary trends it was possible to give a scheme to the mutual relationships of the pollen types. It is concluded that the centre of origin of the family may be Africa. It was pot possible to point to distinct relationships with other families on pollenmorphological data alone.     

Pollen walls of Araceae,with special reference to their fossilization potential

The pollen grains, the pistil, growth of the pollen tube and its pathway are described in Borago officinalis and Heliotropium europaeum. The exine is thick in both taxa but it is covered with dense gemmae in Borago. The intine seems to be thicker and contains more proteins in Borago than in Heliotropium. Starch is very abundant in the latter while it is lacking in the former. The style is hollow in Borago with a stylar canal running from the stigma to the ovary, while in Heliotropium it is broadly cone‐shaped with papillae located at the base of the cone (the “stigmatic ring") and not at the top of the style as usual. In Borago stigmatic papillae are unicellular, skittle‐shaped and have a thick pectocellulosic wall and an equally thick cuticular layer, while in Heliotropium the stigmatic papillae are unicellular, elongated cone‐shaped with a thin pecto‐cellulosic wall and have an apparently reduced cuticular layer. The stigmatic exudate is very abundant on the stigmas of Heliotropium even before anthesis while it is absent on those of Borago except when allo‐pollination occurs. Pollen tube growth has been followed from stigma to ovules in both taxa.     

Pollen and seed morphology of Gueldenstaedtia and Tibetia (Leguminosae) - with a special reference to the taxonomic significance

The pollen morphology of Gueldenstaedtia gansuensis. G. gracilis, G. henryi, G. monophylla. G. mutijlora, G. stenophylla. and G. verna and Tibetia liangshanensis, T. tongolensis, T. yadongensis. T. coelestis, and T yunnanensis are reported for the first time. The seed morphology of G. gracilis, G. maritima. G. monophylla, G. mutiflora, G. taihangensis, and G. verna and L coelestis, T. himalaica, T. yunnanensis, and T. yadongensis are firstly described here. In pollen morphology, the differences of pollen grains of Gueldenstaedtia and Tibetia are as follows: Gueldenstaedtia with pollen grains 3–colporate, psilate, and shapes spheroidal, sometimes subprolate, prolate or oblong; and Tibetia with pollen grains 3– and 4–colporate, perforate, shapes spheroidal, sometimes subprolate or prolate. These results, combined with the data of the basic chromosome number x=7 of Gueldenstaedtia and x=8 of Tibetia, support that the two genera should be recognized as two distinct genera, which are consistent with their morphological characters: Gueldenstaedtia with 2 upper lobes of calyx free, stipules free, adnate to petiole, and Tibetia with 2 upper lobes of calyx connate, stipules connate and opposite to leaves. In Tibetia, two types of pollen grains, 3– and 4–colporate pollen grains, are found. Regarding seed morphology: Gueldenstaedtia has circular depression, irregular circular depression or irregular circular reticulation on the surface; Tibetia has smooth surface. The differences in seed morphology of the two genera also support that they should be kept separate. The pollen morphology supports that G. gansuensis, G. gracilis, G. multiflora, G. stenophylla, and G. verna should be reduced into one species consistent with their morphological characteristics. The pollen grains of G. henryi are different from those of the other species in having wide colpi.     

Pollen carryover,nectar rewards,and pollinator behavior with special reference to Diervilla lonicera

Summary Pollen carryover was measured in three species of bumble bee pollinated plants by counting the numbers of foreign grains applied to the stigmas of a series of flowers by bumble bees. Deposition declined with the number of flowers visited in a roughly exponential fashion; most grains were deposited on the first few flowers, but some grains went much farther, the maximum carryover being 54 flowers. Variation in deposition was very high. In Diervilla lonicera, bees desposited significantly more grains on flowers which contained large amounts of nectar than on drained flowers. The implications are discussed in terms of plant strategies for optimizing pollination.     

Pollen and ovule production in wind-pollinated species with special reference to Juncus

The reproductive biology of wind-pollinated species in terms of pollen and ovule production is rarely studied compared with zoophilous species, despite available hypotheses on the effect of growth form and life-history traits on reproductive investment. Here, we use published data and new data for species of Juncus and Luzula (Juncaceae) to test the hypotheses that, in wind-pollinated species, woody perennials should exhibit larger pollen–ovule (P/O) ratios than herbaceous species and that species with separate sexes have larger P/O ratios than homoecious species. In total, we report pollen and ovule production for 291 wind-pollinated species, including 19 Juncus and 5 Luzula species. Compared with other wind-pollinated species, Juncus exhibits unusually low P/O ratios (log P/O = 2.06 ± 0.46) because of high ovule production. We argue that the high ovule and seed production in Juncus, associated with frequent self-fertilization, may be beneficial in habitats preferred by the genus. In general, we found higher P/O ratios in woody perennials (log P/O = 4.37 ± 1.18) or in species with separate sexes (log P/O = 4.28 ± 1.12) than in herbaceous (log P/O = 3.51 ± 0.77) or homoecious (log P/O = 3.52 ± 0.80) species, respectively. However, when we analyzed woody perennials separately, we found no significant difference in P/O ratios between homoecious and nonhomoecious species. We argue that woody perennials, independent of dicliny, may be preferentially outcrossed and therefore exhibit decreased variation in mating systems compared with herbs. Because the degree of outcrossing correlates with P/O ratios, differences between homoecious and nonhomoecious woody perennials could be less pronounced.     

Functional morphology of the enteric nervous system with special reference to large mammals.

This short review reports the latest insights into the structural organization of the enteric nervous system, with special emphasis on the intrinsic innervation of the intestinal tract of large omnivorous mammals such as the pig. Using various techniques, including lesion experiments, morphological and neurochemical features of distinct neuronal populations as well as the direction of the axonal processes within the different nerve networks could be revealed. Special attention was paid to the considerable species differences in this respect between large omnivorous animals and humans on the one hand and small laboratory animals on the other hand.     

Pollen evolution and systematics inAnnonaceae with special reference to the disulcate Australian endemic genera

All genera ofAnnonaceae endemic in Australia (Ancana, Fitzalania, Haplostichanthus) show almost exactly the same type of disulcate (disulculate) pollen with intact exine extending over the sulci. Tetrad stages inHaplostichanthus andAncana reveal a latudinal subequatiorial orientation of the two sulci at the proximal hemisphere. Sometimes they fuse into a ±zonosulcate aperture.Fissistigma pollen grains are ±globose and have a flattened pole with a central elevation and a concentric groove, covered by a somewhat reduced exine. This palynological characters give further support for separating the generaAncana andFissistigma. Germination was observed inHaplostichanthus where the pollen tube emerges at one of the two sulci and inFissistigma where the flattened part breaks up during germination. The aperture types described here are obviously transitional stages between aperturate and inaperturate pollen grains and are discussed in regard to pollen evolution.     

Morphology and ultrastructure ofOlisthodiscus luteus (Raphidophyceae) with special reference to the taxonomy

A flattened discoid flagellate collected from the Seto Inland Sea, Japan, has been examined by light and electron microscopy. This alga agrees well withClisthodiscus luteus Carter. It has two heterodynamic flagella emerging from a furrow on the upward side of the cell that contains six to 13 yellow-green parietal chloroplasts. It does not rotate but smoothly glide while swimming. The cell has a thin periplast lying between the plasmalemma and chloroplasts. Neither lipid bodies nor mucocysts are seen in the periplast. The pyrenoid matrix being free from thylakoids is penetrated by several cytoplasmic canals from various directions. There are no vesicles of periplastidal network in the narrow space between chloroplast envelope and chloroplast ER. The ultrastructural features ofO. luteus are unique, sharing certain characters with the raphidophycean algae but others withPseudopedinella pyriformis, a unique member of the Chrysophyceae.     

Ontogeny and cranial morphology of the tympanic region of the Tupaiidae, with special reference to Ptilocercus

The structure of the tympanic region of the skull of Ptilocercus lowii was studied in an embryo of 30 mm crown-rump length and in 5 osteocrania. As in Tupaia, the anterior wall of the bulla of Ptilocercus is not completed by a tympanic process of the alisphenoid, contrary to earlier reports. Ptilocercus resembles Tupaia in the following derived characters. The ventral wall of the tympanic cavity is formed by a rostral entotympanic and by a caudal tympanic process of the petrosal. The entotympanic develops in primary connection with the tubal cartilage. The tympanic aperture of the auditory tube is bordered by the entotympanic. The ring-shaped tympanicum is covered by the entotympanicum and is aphaneric. The musculus tensor tympani is lacking. Among mammals, these characters can be regarded as synapomorphic for the Tupaiidae, that is, to have been present in the common ancestor of the two subfamilies. From the evidence of the tympanic region, the Tupaiidae, therefore, form a monophyletic group. Besides these synapomorphies, there are remarkable differences between Ptilocercus and Tupaia in the structure of the bulla. In Ptilocercus the bulla is smaller and less pneumatized than in Tupaia. An anterior intrabullar septum, present in Tupaia, is lacking in Ptilocercus. The epitympanic wing of the alisphenoid is smaller in Ptilocercus than in Tupaia. A lateral prefacial commissure of the tegmen tympani is present in Ptilocercus, but absent in Tupaia. The caudal tympanic process of the petrosal is larger in Ptilocercus than in Tupaia. These characters are autapomorphic for the Ptilocercinae and for the Tupaiinae, respectively. They demonstrate that the auditory bulla of Ptilocercus and that of Tupaia have evolved independently to a considerable extent. An early phylogenetic separation of their respective ancestors seems likely. The tympanic region of the skull provides no evidence for close relationships of the tree shrews to the primates or to any other eutherians. The classification of the Tupaiidae in a separate order, Scandentia, is supported.     

Surface ultrastructure of the gill arch of the killifish, Fundulus heteroclitus, from seawater and freshwater, with special reference to the morphology of apical crypts of chloride cells

The surface ultrastructure of the gill arches of the killifish, Fundulus heteroclitus, adapted to seawater or freshwater, was found to be similar to that reported for other euryhaline teleosts. Two rows of gill filaments (about 42 filaments per row) extended posterolaterally, and two rows of gill rakers (about 10 rakers per row) extended anteromedially from each arch. Leaf-like respiratory lamellae protruded along both sides of each filament, from its base to its apex. The distributions, sizes, and numbers of various surface cells and structures were also determined. All surfaces were covered by a mosaic of pavement cells, which measured about 7 X 4 microns and exhibited concentrically arranged surface ridges. Taste buds were especially prominent on the rakers and the pharyngeal surfaces of the first and second gill arches, but were often replaced by horny spines on the third and fourth gill arches. Apical crypts of chloride cells occurred mostly on the surfaces of the gill filaments adjacent to the afferent artery of the filament. In seawater adapted killifish, crypts resembled narrow, deep holes along the borders of adjacent pavement cells, had openings of about 2 microns2, and occurred at a frequency of about 1 per 70 microns2 of surface area. In freshwater fish, the crypts usually had larger openings (about 10 microns2), occurred less frequently (1 per 123 microns2), and exhibited many cellular projections in their interiors. Changes in crypt morphology may be related to the ion transport function of chloride cells.     

Vischeria stellata (Eustigmatophyceae): ultrastructure of the zoospores,with special reference to the flagellar apparatus

Summary Ultrastructure of the zoospores ofVischeria stellata (R. Chodat ex Poulton) Pascher is investigated, with particular reference to the system of flagellar roots. Microtubular roots and a rhizoplast are present and a model showing their distribution is proposed. Four microtubular roots attach to the basal bodies in a system basically similar to that displayed by the heterokont algae and fungi. The rhizoplast is also similar to that of other heterokont algae. We conclude from these observations that the class Eustigmatophyceae should be placed within the division Heterokontophyta.Abbreviations C chloroplast - B basal body of the emergent flagellum - B' second basal body - E eyespot - F emergent flagellum - FS flagellar swelling - LV lamellate vesicle - M mastigonemes - MTs microtubules - N nucleus - R 1–R 4 microtubular roots - Rh rhizoplast - SB striated band - SV spiral vesicle     

Pollen morphology of the genus Orobanche L. (Orobanchaceae)

A comparative palynological study of 25 taxa of the genus Orobanche L. belonging to section Trionychon Wallr. and section Orobanche L. was carried out. A clear difference between the pollen grains of section Trionychon and section Orobanche was observed. The grains of section Trionychon are typically tricolpate, radially symmetrical, more or less oblate spheroidal, with a microreticulate, or scabrate-perforate sculpture. Section Orobanche on the other hand, had spheroidal, more or less inaperturate pollen grains, although some were tricolpate, but without any clear symmetry. The basic surface sculpture of the pollen in section Orobanche was scabrate to rugulate-perforate. Palynoiogicaliy, six groups can be recognized amongst the species of the genus Orobanche , lor which a key is provided.     

The gas bladder of Argentina silus L., with special reference to the ultrastructure of the gas gland cells and the countercurrent vascular bundles

Summary The orifice between the two chambers of the gas bladder in Argentina silus is surrounded by a sphincter muscle. Gas analyses of the gas bladder contents of fish from 400 meters depth give 0–1% carbon dioxide and 9–72% oxygen. Micro-retia mirabilia form a countercurrent vascular system, and the arterial component has peripherally a sphincter mechanism. The function of the glandular layer of the anterior chamber remains uncertain, but the structure indicates secretion into blood capillaries. The lining epithelium of the anterior chamber may secrete some substance into blood or directly into the lumen, which may be involved in a secretory mechanism. This conclusion is not supported by our histochemical tests. The posterior chamber has no micro-retia and the blood vessels have a different origin from those of the anterior chamber. The blood vessels form a plexus of capillaries or sinuses in contact with the flat lining epithelium, thus allowing gases to pass freely by diffusion. — The muscular layers of both chambers are innervated by catecholamine-containing nerve fibres.The investigation was supported by grants from the Swedish Natural Research Council (No. 99-35) and by the Faculty of Mathematics and Science, University of Lund.