THE ANATOMY OF PACHYDERMIA LAEVIS (ARCHAEOGASTROPODA: 'PELTOSPIRIDAE')

The anatomy of Pachydermia laevis Warén & Bouchet,1989 is investigated. It is a deep-sea gastropod and restrictedto hydrothermal vents of the East Pacific Rise. Its anatomyresembles that of Melanodrymia aurantiaca Hickman, 1984 (Melanodrymiidae)in most respects, except that its gonopericardial duct opensinto the renopericardial duct, not into the peri-cardial chamber,and that it lacks a copulatory organ. Examination of M. aurantiacamain confirms earlier work. The two species have a cerebralbuccal connective fused with the cerebral ganglion (not freefrom it), a synapomorphy that has not been described for anyother archaeogastropod. The investigation suggests that Melanodrymiaand Pachydermia are closely related and together with Cyathermiidaeand Neomphalidae form a monophyletic group within the Neomphalina.No evidence was found to support earlier speculations aboutclose relations of Neomphalina to Viviparoidea. (Received 10 January 1996; accepted 3 April 1997)     

THE ANATOMY AND RELATIONSHIPS OF THE ORBITESTELLIDAE (GASTROPODA: HETEROBRANCHIA)

The anatomy of two genera of the marine gastropod family, Orbitestellidae,Orbitestella and Microdiscula, is described. They possess apigmented mantle gland and pallial renal organ, lack a ctenidiumand have a simple hermaphrodite genital system with an externalpenis. They lack buccal cartilages, have a simple oesophagus,a massive jaw and a crystalline style in the stomach. The Orbitestellidaeare shown to be primitive heterobranchs, perhaps related tothe northern-hemisphere freshwater family Valvatidae. (Received 9 September 1989; accepted 30 December 1989)     

THE ANATOMY AND RELATIONSHIPS OF ELACHISINA DALL (GASTROPODA: RISSOACEA)

Species of Elachisina are marine and extend from the Caribbeanand western North and Central America to the Philippines, Hawaiiand New Zealand. The anatomy and other morphological featuresof Elachisina ( = Microdocluis) floridana (Rehder) from theFlorida Keys are described and compared with rissoacean familiesjudged to be most closely allied. This species has a uniquecombination of characters which do not correspond to those character-setsused to define any known rissoacean family. Important featuresinclude a metapodial as well as pallial tentacles, a wide ctenidiumwith low, triangular filaments, an osphradium which is shortrelative to the ctenidium, an S-shaped loop of the intestinewhich extends into the pallial roof, long dorsal folds in themidoesophagus, a rather loosely organised nervous system, anopen prostate gland from which the pallial vas deferens exitsat its anterior extremity, glandular lobes on the penis, a non-glandularfold on the right side of the ventral channel of the capsulegland and a fold on the left side in the posterior end of thechannel, a pair of seminal receptacles lying between the albumenand capsule glands, a bursa which lies alongside the capsulegland and opens posteriorly to the ventral channel and a U-shaped,expanded section of the oviduct proximal to the albumen glandand seminal receptacles. This combination of characters is consideredto be sufficiently distinct to arrant the erection of a newfamily-level taxon to accommodate the small group of speciesjudged to be congeneric with E. floridana. The Elachisinidaeappears to be most closely related to the Rissoidae, Iravadiidaeand Hydrobiidae. (Received 19 October 1983;     

COMPARATIVE ANATOMY OF THE PETIOLE AND INFRAGENERIC RELATIONSHIPS IN JATROPHA (EUPHORBIACEAE)

Anatomical features of the petiole in several species of Jatropha L. (Euphorbiaceae) are presented as evidence in support of infrageneric relationships. A trilacunar 3-trace nodal pattern is typical for the genus. The vascular supply to the stipules is derived from the branching of the two peripheral leaf traces. The number of vascular bundles range from 11 through 9, 7, 5 and 3, and occur in a ring, as free traces, a medullated cylinder, or as U-shaped free traces. The reduction from nine to three bundles is correlated with the gross morphological features while 11, which occurs only in the section Peltatae (Pax) Dehgan & Webster, presents an increase. Reduction in the number of petiolar traces follows the evolutionary advancement of various taxa. This reduction in traces corresponds with south-north distribution of the species and consequential adaptation to colder and more arid climates in Central America and Africa. Smaller leaves, fewer primary veins and fewer vascular traces have resulted as a response to reduced need for water. Presence of dorsal (super-numerary) bundles which supply the petiolar glands in subgenus Jatropha (= Adenoropium Pax) is considered significant, since African taxa of the section (subsection Pubescentes Pax) have retained these bundles despite the loss of petiolar glands. The latter glands are prominent in the South American and Indian species. Sectional lines in the genus can, therefore, be drawn generally on the basis of numerical constancy and relative uniformity in the arrangement of petiolar traces. The continuity of vascular bundles from the stem into the petiole and variations of bundle arrangements are depicted in three-dimensional drawings.     

THE ANATOMY AND RELATIONSHIPS OF A MARINE VALVATOIDEAN (GASTROPODA: HETEROBRANCHIA)

The anatomy of Cornirostra (new genus) pellucida (Laseron),a marine Indo-West Pacific gastropod, is described and is shownto be similar to that of the northern hemisphere, freshwaterValvatidae. There are, however, several differences betweenCornirostra and valvatids, notably in details of the anatomyof the reproductive system, the morphology of the head-foot,the spawn and in radular characters that warrant family-levelseparation for Cornirostra. Tomura bicaudata (Pilsbry and McGinty) from Florida is alsoa member of the family. (Received 9 September 1989; accepted 30 December 1989)     

WOOD ANATOMY AND RELATIONSHIPS OF LACTORIDACEAE

Mature wood of Lactoris, not previously available for study, reveals ten distinctive characters: vessels with simple perforation plates; vessels in pore multiples; vessel-to-axial parenchyma pits scalariform or transitional, vessel-to-vessel pits alternate; fiber-tracheids with vestigial pits; fiber-tracheids, vessels, and axial parenchyma storied; axial parenchyma vasicentric scanty; axial parenchyma either not subdivided or, if subdivided, with thin nonlignified walls between the cells (like the septa in septate fibers); rays wide and tall, little altered during ontogeny; ray cells upright; and ray cells taller adjacent to fascicular areas. All of these features occur in woods of Piper and other Piperaceae. The systematic position of Lactoris is therefore reassessed. Evidence available to date is consonant with placement of Lactoridaceae in Piperales, in which it would be more primitive than Piperaceae or Saururaceae. Features cited as evidence for alternative placements of Lactoridaceae are reviewed.     

THE ANATOMY AND RELATIONSHIPS OF HYDROCOCCUS BRAZIERI (T. WOODS): Mollusca: Gastropoda: Rissoacea

Hydrococcus brazieri is an abundant, small gastropod which livesin brackish habitats on intertidal mud flats along the westernand southern coasts of Australia. It is typical of the Rissoaceain basic morphology but has a unique combination of charactersthat suggest it should be placed in a separate family, the HydrococcidaeThiele, 1928. The final assessment of the relationships of Hydrococcusmust, however, await more detailed information about relatedfamilies. The distinctive characters of Hydrococcus includea multispiral operculum with a central nucleus, a long, posteriorpallial tentacle with a short tentacle at its base, no metapodialtentacle, a penis bearing two accessory lobes, a bursa copulatrixwhich opens directly into the mantle cavity independently ofthe oviduct opening and rather long connectives between boththe pleural and oesophageal ganglia. There is no ctenidium butfolds on the pallial roof probably have a respiratory function. Hydrococcus graniformis Thiele and Ampullarina minuta T. Woodsare shown to be synonyms of Rissoina brazieri T. Woods. A clinebetween the forms typical of brazieri and graniformis is demonstrated. (Received 20 November 1980;     

THE SYSTEMATICS AND ANATOMY OF GONGYLOCARPUS (ONAGRACEAE)

The unique fruiting structures of the closely related, principally Mexican, monotypic genera Gongylocarpus and Burragea (Onagraceae) compelled a detailed anatomical and cytological investigation of these plants which led to the conclusion that they should be included in a single genus, Gongylocarpus. Gongylocarpus fruticulosus (Burragea), endemic to two adjacent islands off the west coast of Baja California, is divided into two subspecies, subsp. fruticulosus and subsp. glaber. The vegetative and floral anatomy, including wood anatomy, of both species is described. The fruits of these two species grow into the stem by meristematic activity during the course of ontogeny, the ovaries in the mature flower being superficial and sessile in the leaf axil. There is no pedicel associated with the flower, but only a branch gap. Meristematic tissue at the base of the locules divides rapidly at a relatively late ontogenetic stage, the ovaries growing downward into the stem and crushing the pith. The mature, heavily sclerenchymatous fruits are located wholly within the stem, and in G. fruticulosus they are aggregated into long chains. Both species have a gametic chromosome number of n = 11, a characteristic otherwise unknown in the tribe Onagreae but shared with other generalized groups in the family. Taken together with other features, this suggests a primitive position within the tribe for Gongylocarpus.     

ANATOMY AND RELATIONSHIPS OF SOME DEVONIAN PROGYMNOSPERMS FROM NEW YORK

New specimens of Triloboxylon ashlandicum Matten and Banks (1966) show additional features of the anatomy and morphology of the plant. The primary xylem has strands of parenchyma associated with trace formation. Secondary xylem and phloem are described for the first time. The outer cortex, previously unknown, contains hypodermal fiber strands. The ultimate appendages are much divided and planated. Specimens of Aneurophyton hallii (Arnold, 1940) were reexamined and newly prepared. They are transferred to the genus Triloboxylon as T. hallii. Triloboxylon is transferred from Pteropsida-Incertae Sedis to the Aneurophytales. New information on the morphology and anatomy of Telraxylopteris is presented and its identity to Sphenoxylon is supported.     

THE MORPHOLOGY AND RELATIONSHIPS OF DALECHAMPIA SCANDENS (EUPHORBIACEAE)

The circumtropical but preponderantly American genus Dalechampia, comprising nearly 100 species of twining vines (or rarely subshrubs), is strikingly isolated within the Euphorbiaceae because of its distinctive bibracteate inflorescences. There has been considerable taxonomic controversy with regard to the relationships of the genus, and it has been suggested that Dalechampia is allied to the tribe Euphorbieae because of a supposed analogy between its inflorescence and the cyathium in the Euphorbieae. Field and laboratory investigations of the common American species D. scandens, together with a comparative survey of related species, have thrown some light on these problems. The Dalechampia inflorescence seems best interpreted as consisting of a terminal staminate pleiochasium (with part of the lateral branches transformed for nectar production), juxtaposed to a 3-flowered pistillate cyme. The lips of the conspicuous bilabiate involucre are formed by the hypertrophied bracts which subtend the staminate and pistillate cymes. The bisexual inflorescences appear to be distinctly proterogynous, rather than proterandrous, as has been previously suggested. The configuration of the inflorescence—a bilaterally symmetrical pseudanthium—suggests adaptation for crosspollination, but the closing movement of the bracts makes self-pollination probable in the absence of visits by pollinators. The similarity of the Dalechampia inflorescence to the cyathium of the Euphorbieae appears to be entirely superficial, and both reproductive and vegetative data suggest that Dalechampia is related to taxa of tribe Plukenetieae.     

THE ORIGIN AND RELATIONSHIPS OF LASTHENIA BURKEI (COMPOSITAE)

Lasthenia burkei (Compositae) is a narrowly restricted California endemic closely related to L. conjugens and L. fremontii. These three species differ from each other by pappus and phyllary characters and in geographical distribution. All are freely intercrossable, but L. fremontii forms rather sterile artificial hybrids with its two relatives which, in turn, form fairly fertile artificial hybrids with each other. Lasthenia burkei and L. conjugens have homologous chromosomes, four of which are homologous with four of those of L. fremontii. The remaining two chromosomes probably have reciprocal translocations which lead to multivalent formation during meiosis in interspecific hybrids. Pollen viability is restored in most F₂ generations, suggesting a close genetic relationship among the three species. The evolutionary relationship among these species may be a linear one with L. burkei occupying an intermediate position between L. fremontii and L. conjugens, although the direction of this linear phylogeny is not certain, or it may be one in which L. burkei has been derived from hybridization between its two relatives. Support for the latter hypothesis comes from the appearance of some individuals in F₁ progenies of L. conjugens × L. fremontii that are morphologically indistinguishable from L. burkei (although fairly sterile). The apparently rather simple genetic basis for the morphological characteristics of each of the species in this trio suggests that the morphologically heterogeneous genus Lasthenia may be considerably more homogeneous genetically than might be suspected. Because of the diverse kinds of relationships among these three Lasthenias, possible alternative taxonomies for the group are dependent upon those relationships that a taxonomist wishes to communicate. Nevertheless, the patterns of diversification in this group have led to reaffirmation of an earlier decision that three species should be recognized.     

THE ECOLOGY OF THE HONG KONG LIMPETS CELLANA GRATA (GOULD, 1859) AND PATELLOIDA PYGMAEA(DUNKER, 1860): DISTRIBUTION AND POPULATION DYNAMICS

Cellana grata is a high-zoned, exposed-shore limpet with a lifespanof 3 years. Patclloida pygmaeais a low-zoned, sheltered-shorelimpet with a lifespan of I year. C. grata migrates up-shorein winter, but occurs lower on the shore in summer. This migrationis synchronized with variations in algal availability high onthe shore; such variations are, however, themselves relatedto seasonal changes in wave height. P. pygmaea is restrictedto the low shore, year round. The movements upwards in winterand downwards in summer are still evident. Algal species richnessincreased from September to reach a peak between December andMarch, and to abruptly diminish between May and June. The encrustingalgae Brachytrichia maculans, Hildenbrandia prototypus, Lithothamnionsp. and Ralfsia vcrrucosa were present year round. The timingof juvenile recruitment of C. grata and P. pygmaea was fromOctober to July and February to October, respectively. Temperaturemay be important in enhancing juvenile survival by affectingthe seasonal pattern of algal occurrence on the shore. Seasonalfluctuations in the rate of growth were recorded for both specieswith the time of fastest growth of C. grata and P. pygmaea occurringbetween October and March and September and February, respectively.Mortality of both species occurred mainly in summer. Summerheat, predation and intra-specific competition for food appearto be the major causes of death. (Received 1 December 1992; accepted 5 May 1993)     

POLLEN MORPHOLOGY,TRICHOME TYPES,AND RELATIONSHIPS OF THE GRONOVIOIDEAE (LOASACEAE)

The pollen of all four genera of Gronovioideae—Cevallia, Fuertesia, Gronovia, and Petalonyx—was examined in light microscopy, and scanning and transmission electron microscopy. The pollen of Cevallia, of Fuertesia, and of Gronovia can be easily distinguished from each other and from all remaining Loasaceae. Only Petalonyx, with a striate tectum, shows a clear relationship to the Mentzelioideae and Loasoideae, the vast majority of which have striate-reticulate or striate tecta. The trichome data are mostly congruent with the pollen data: Cevallia, Fuertesia, and Gronovia each have a distinctive trichome not known to occur elsewhere in the family, while Petalonyx has only the common types. A cladistic analysis of Gronovioideae utilizing Mentzelia as the outgroup proposes that Cevallia, Gronovia, and Fuertesia are a sister group to Petalonyx within the subfamily. The relationships of the four genera to each other and of Gronovioideae to the Loasaceae are discussed.     

MORPHOLOGY AND ANATOMY OF THE LEAF OF COLEUS BLUMEI (LAMIACEAE)

Leaves of the Princeton and a variegated clone of Coleus blumei Benth. were examined with the light microscope to determine the course of their vasculature and the spatial relationship between the mesophyll, bundle sheath, and vascular tissues. In Princeton clone leaves two leaf traces enter the petiole at the node and quickly branch to form an arc of bundles which undergo further divisions as well as fusions in the distal half of the petiole. The anastomosing arc of bundles reaches its greatest complexity in the base of the midvein, where its lateral-most bundles unite and diverge outward to form secondary veins. As the midvein bundles continue acropetally, they gradually fuse more and divide less until only a single bundle remains, from which secondaries and smaller veins branch. Major (ribbed) veins include not only the midvein and secondaries but also tertiary and quaternary veins. Decreasing vein size is accompanied by increasing direct contact between vascular and photosynthetic tissues. Minor veins, which make up 86% of the total vein length, are completely surrounded by photosynthetic bundle sheaths and mesophyll consisting of palisade and spongy parenchyma. Statoliths occur in a layer of cells just outside the phloem of the petiole-midrib axis and secondary veins. Functional hydathodes are present at the apices of the marginal teeth. The overall organization of tissues in variegated leaves differs little in either the green or albuminous areas from corresponding (but always green) regions of Princeton leaves. Chloroplasts are lacking in mesophyll, bundle-sheath, and most guard cells of the albuminous region but are present in guard cells which are within 1 mm of green areas.     

REPRODUCTIVE BIOLOGY OF WEEDY AND CULTIVATED MIRABILIS (NYCTAGINACEAE)

The reproductive biology of Mirabilis nyctaginea (Michx.) MacM. contributes to the plant's success as a weed and invader of disturbed habitats whereas that of M. Jalapa L. reflects its success as a cultivar. Plants of M. nyctaginea flowering in early summer produce chasmogamous flowers whereas plants flowering in late summer produce cleistogamous flowers. Plants of both species are self-compatible and flower behavior contributes to self-pollination. The flowers open late in the afternoon and close late the following morning. In M. nyctaginea flowers are effectively pollinated by bees both in the afternoon and morning, and during the night moths are effective pollinators. Mirabilis Jalapa is self-pollinating. Anther closure during rain showers, a result of water droplets falling into open anthers, minimizes pollen loss and is highly adaptive. The reproductive biology of M. nyctaginea and M. Jalapa is contrasted with that of the obligate outcrossing species M. multiflora (Torr.) Gray and M. froebelii (Behr) Greene.     

ONTOGENY AND ANATOMY OF THE FLOWER OF LIMNOCHARIS FLAVA (BUTOMACEAE)

The flowers of Limnocharis flava (L.) Buch. are borne in an indeterminate umbel and each consists of three sepals, three yellow petals, and about 18 carpels surrounded by numerous stamens and staminodia. The androecium is centrifugally developed, and the last-formed members are staminodial; it is supplied by branching vascular systems. Carpels arise almost simultaneously, and a prominent residual floral apex remains. The carpels are partially conduplicately closed and are also primitive in possessing laminar placentation and in lacking differentiation of a style. The gynoecium is essentially apocarpous, but there are slight fusions of adjacent carpels near their ventral margins where they are attached to the receptacle. It is suggested that the Limnocharis flower is the most primitive in the family.     

FUNCTIONAL AND EVOLUTIONARY ASPECTS OF THE POSTCRANIAL ANATOMY OF DICYNODONTS (SYNAPSIDA, THERAPSIDA)

Abstract:  Restoration of the major skeletal muscles and functional morphological analysis of the postcranium were carried out on two Triassic dicynodont genera, Wadiasaurus and Lystrosaurus . A phylogenetic analysis of 12 selected Permian and Triassic dicynodont taxa was conducted and the postcranial character states were then mapped onto the most parsimonious tree. The analysis revealed changes in pectoral girdle and forelimb morphology, which included reduction of the coracoid plate, increasing robustness of the deltopectoral crest, change in humeral orientation from lateral to caudolateral, increasing prominence of the humeral head, and increasing robustness of the radius. Such changes can be associated with a functional tendency to reduce the lateral component of the propulsive force while still in an abducted mode. On the other hand, changes associated with the pelvic girdle included expansion of the preacetabular iliac process, reduction of the postacetabular iliac process, craniocaudal expansion of the iliac blade, change in the shape of the pubis from flat and plate-like to small and rod-like with a cranial process, and change in acetabular orientation from lateral to caudolateral. The femoral head, starting from a cranioproximal position, progressively became dorsally pronounced and offset from the body. Other features/changes associated with the femur included increasing robustness of the trochanter major, and increasing flattening of the femoral midshaft. Changes in the axial skeleton included increasing stiffening of the trunk to reduce lateral undulations, increasing dorsoventral flexion, and increasing sacral vertebral count, which can be correlated with the preacetabular iliac expansion. These findings suggest that the dicynodont postcranial skeleton evolved towards more upright hindlimb morphology with the body held well off the ground.