Operculum development in theEudesmieae B eucalypts andEucalyptus caesia (Myrtaceae)

In theEudesmieae B eucalypts and inEucalyptus caesia, the perianth of the mature flower consists of a single, anatomically continuous, opercular structure that is crowned by the tips of the original free and separate calycine and corolline whorls. Ontogenetic and comparative evidence supports the hypothesis that this operculum is mostly corolline in composition, and that the calycine parts have been elevated distally onto the dorsal surface. In theEudesmieae B eucalypts this condition appears to be due to precocious initiation of the corolline primordia, followed by expansion and continuity of their growth centres which incorporates the areas at or below the base of the still differentiating calycine whorl. InEucalyptus caesia the corolline primordia are not precocious, but a similar situation is effected by a seemingly retarded increase in receptacle diameter relative to lateral expansion of the corolline growth centre(s). In these two examples the same final perianth form apparently derives from two different sets of growth processes which, nonetheless, result in the same allometric relationships within the developing flower. Although identical at maturity, the operculum form in these two taxa is best described in terms of convergence, rather than homology.     

Perianth development inAngophora and the bloodwood Eucalypts (Myrtaceae)

The petals ofAngophora flowers are compound structures consisting of two morphologically distinct components that develop along separate morphogenetic pathways. These two components are also evident in the corolline parts of the bloodwood eucalypts. In occasional flowers ofAngophora and some bloodwoods, several adjacent corolline primordia may become continuous due to interprimordial growth, but the petals are mostly free at anthesis. In other bloodwood eucalypt species all the primordia in the corolline whorl become continuous at some stage in development, resulting in an operculum that is anatomically unresolvable into its original petaline parts. The varying degrees of this continuity that are evident within individual trees (and even within single flowers) suggests that operculum formation is an epigenetic event that is determined by morphogenetic processes within the flower. It is suggested that these may relate to differing rates of growth in different regions of the bud.     

Operculum development inEucalyptus clöeziana andEucalyptus informal subg.Monocalyptus (Myrtaceae)

Flowers ofEucalyptus clöeziana have two clearly distinct perianth whorls. The small free parts of the outer (calycine) whorl cease growth early and are lost from the flower; the parts of the inner (corolline) whorl become continuous laterally by confluence of growth centres and form an operculum in the mature flower. The stamens are inserted on a circumfloral buttress (staminophore) that is homologous to the adaxial corolline component inAngophora and the bloodwood andEudesmia eucalypts. Flowers ofMonocalyptus have only one perianth whorl, which is opercular. The stamens are similarly inserted on a circumfloral buttress. Developmental study does not provide conclusive evidence for either a calycine or corolline determination of theMonocalyptus operculum, but comparison with other eucalypt groups, includingE. clöeziana (the sister taxon), predicts an essentially corolline composition.     

Problems of species and genera inEucalyptus (Myrtaceae)

Eucalyptus is recognised as containing somewhat more than 450 species, but this number could reasonably be either decreased or increased considerably by slight variations of species concept. Recognition of taxa, at least in the wild, is less difficult than supposed but their ranking depends on degree and nature of discontinuities or steepened gradients of correlated variation, in this group of diploid sexual outbreeding trees of the dominant stratum. Some 8–10 rather distinct lines marked by different character constellations are discernible inEucalyptus s. lat. (incl.Angophora), and it is clear that the floral operculum is of diverse nature and multiple origin. The advisability of recognising several distinct genera depends on the wideness of polyphylesis in relation to other Myrtaceous genera, and (unfortunately) on practical convenience.Presented at the symposium Speciation and the Species Concept during the XIIth International Botanical Congress, Leningrad, July 8, 1975.     

Evolutionary trends in the androecium of theOrchidaceae

The evolution of the androecium in theOrchidaceae shows three major trends. There is a progressive trend in the degree of fusion of the filament(s) and staminode(s) to the gynoecium. Secondly, there is a reduction in the number of fertile anthers. Finally, there is a progressive change in the position of the base of the anther relative to the apex of the stigma; in the more primitive orchids the apex of the stigma is always higher than the base of the anther (this position is reversed in the higher orchids). All three trends reflect variation in the evolution of pollen dispersal and pollen reception mechanisms in theOrchidaceae. Trends in the evolution of the orchid anther(s) tend to parallel trends in the evolution of their pollinaria.     

Aspects of floral structure and phenology in the genusConophytum (Mesembryanthemaceae)

The complex floral structure in the southern African genusConophytum (Mesembryanthemaceae; 77 spp.) is described in detail and assigned to three basic floral types, two of which can be divided into two subtypes. Correlations between structural features and phenological patterns are demonstrated and discussed in the family context as well as in relation to the systematic subdivision of the genus.     

Early floral development and androecium organization in Fouquieriaceae (Ericales)

Early floral development with focus on the androecium was studied with the help of scanning electron microscopy and serial microtome sectioning in Fouquieria columnaris and F. splendens. Perianth organs appear in a spiral pattern on the floral apex. The spiral may be a clockwise or anti-clockwise. The androecium is best interpreted as two-whorled with all the stamens arranged in a single series. In F. splendens, two or more of the five epipetalous stamen positions are doubled, i.e. they are occupied by stamen pairs. Unusual features in the floral development of Fouquieriaceae include (1) a strong spiral component even in whorled organ categories and (2) a pronouncedly asymmetric floral apex during an early phase of floral development. From a phylogenetic point of view, it seems plausible that the common ancestor of Fouquieriaceae and its sister family Polemoniaceae was characterized by two alternating, pentamerous stamen-whorls.     

Ontogeny, anatomy and systematic significance of ovular structures in the `eucalypt group' (Eucalypteae, Myrtaceae)

Development of ovular structures in the `eucalypt group' (Eucalyteae, Myrtaceae) was investigated using scanning electron microscopy and light microscopy. Different modes of placental expansion account for the variation in initiation and arrangement of ovules and ovulodes. In Eucalyptus sensu stricto placental elongation proceeds proximally and the distally-positioned ovulodes develop from the first primordia initiated (congenital ovulodes). In Angophora, Corymbia, Arillastrum, Allosyncarpia and Stockwellia placental elongation is bi-directional and the ovulodes develop from last-initiated primordia (residual ovulodes). Bi-directional elongation and residual ovulodes are present in the outgroup taxon Lophostemon confertus and is presumably plesiomorphic. This suite of characters is potentially informative for resolving relationships for several key taxa: E. microcorys (subgenus Symphyomyrtus) has proximal placental expansion and congenital ovulodes, which is consistent with most Eucalyptus; E. curtisii (subgenus Gaubaea) has the plesiomophic condition and may be sister to all other species of Eucalyptus.     

Corolla wilting facilitates delayed autonomous self-pollination in Pedicularis dunniana (Orobanchaceae)

Structural changes associated with corolla wilting may serve as a mechanism for effecting self-pollination. Low pollinator visitation, high seed production and a corolla that persists after anthesis indicates that Pedicularis dunniana is autogamous. Delayed autonomous self-pollination is facilitated by corolla wilting. Wilting of the upper lip (galea) brought the pollen laden anthers into contact with the stigma resulting in the deposition of self pollen on the stigma. The seed set of flowers either emasculated, or with restrained galeae thus preventing anthers brushing against the stigma, was significantly lower than that of open-pollinated flowers. This demonstrates that autogamy occurs in this species through corolla wilting. Germination experiments indicated that outcross seedlings were more vigorous than selfed seedlings as a result of inbreeding depression. It is likely that autogamy provides reproductive assurance for P. dunniana under conditions of pollinator scarcity.     

A phylogenetic and allozyme approach to understanding rarity in three “green ash” eucalypts (Myrtaceae)

Phylogenetic relationships among the 12 species of the green ash group of eucalypts were examined using allozyme data, to investigate the causes of rarity in three localized endemics of the group. The relationships suggested by the allozyme data showed both similarities to and differences from those estimated from morphological data byLadiges and coworkers. The phylogenetic relationships suggest that rarity inEucalyptus burgessiana may be related to recent divergence, whileE. paliformis andE. rupicola are relatively old species, more likely to be relicts, and/or restricted to a rare habitat.     

Variation within and among the chloroplast genomes ofMelaleuca alternifolia andM. linariifolia (Myrtaceae)

Melaleuca alternifolia andM. linariifolia are commercially important Australian species harvested for their essential oils. Both species have relatively narrow and disjunct distributions on the central coast of eastern Australia. Variation in the chloroplast genome was assessed for eight individuals from each of twelve populations, representing the species' geographic range. Low nucleotide diversity withinM. alternifolia contrasted with high nucleotide diversity inM. linariifolia. CpDNA data are consistent with the southern population ofM. alternifolia being a hybrid population withM. linariifolia. The two species are sympatric in this region. Variation inM. linariifolia was geographically structured, with northern populations differing from southern populations by seven restriction site mutations, five length mutations and an inversion. There was no evidence of hybridisation of the cp genome of northernM. linariifolia with the partially sympatric speciesM. trichostachya. Intra- and interspecific variation in the chloroplast genomes ofM. alternifolia, M. linariifolia, andM. trichostachya indicate considerable potential for the use of intraspecific cpDNA studies in examining phylogenetic relationships in melaleucas.     

Carbon fixation in eucalypts in the field

Summary The rate of CO₂ assimilation at light saturation and an intercellular CO₂ concentration of 350 l l^-1 (photosynthetic capacity), measured in leaves of Eucalyptus pauciflora, E. behriana, E. delegatensis and Acacia melanoxylon, declined over the course of cloudless days under naturally varying environmental conditions as well as under constant optimal conditions for high CO₂ uptake. Since the capacity did not recover during the light period, it was different from the midday depression of gas exchange. The change appeared to be caused neither by the diurnal variation of total leaf water potential, by photoinhibition of redox-reaction centres in photosystems nor by changes in the intrinsic properties of Ribulose-bisphosphate carboxylase-oxygenase. The decline was more pronounced in winter than in summer. It was related to the duration of illumination or the cumulative carbon gain. It was reversible in the following dark phase, and it did not occur on changeable days with short peaks of high light.Despite the decline in photosynthetic capacity, the initial slope of the CO₂ response of net photosynthesis, as obtained at low intercellular CO₂ concentrations, remained constant during the day, but declined at night when photosynthetic capacity recovered. In all cases stomatal conductance varied in parallel with photosynthetic capacity. The relevance of changes in photosynthetic capacity for the intercellular CO₂ concentration is discussed.Abbreviations and symbols A CO₂ assimilation - ABA abscisic acid - A_c350 photosynthetic capacity at c_i=350l l^-1 - c_i intercellular CO₂ concentration - g leaf conductance to water vapour - I photon flux density (irradiance) - P air pressure - P_i inorganic phosphate - R_d net CO₂ release at _* - Rubisco Ribulose-bisphosphate carboxylase-oxygenase - RuBP Ribulose-bisphosphate - T leaf temperature - w leaf-to-air water vapour concentration difference - A/c_i carboxylation efficiency at low c_i - _* light-independent CO₂ compensation point - total leaf water potential     

New species ofBeaufortia andChamaelaucium (Myrtaceae),Drosera (Droseraceae) andPultenaea (Fabaceae) from SW. Australia

Four new species of the generaBeaufortia, Chamaelaucium, Drosera, andPultenaea are described based on the author's collections from SW. Australia. Their affinities are discussed and full illustrations are provided.Dedicated to Hofrat Univ.-Prof.K. H. Rechinger on the occasion of his 80th birthday.     

Estimates of hierarchical variation in flower morphology in natural populations ofScleranthus annuus (Caryophyllaceae), an inbreeding annual

The variation in two sets of morphological characters of the flowers of the highly inbreedingScleranthus annuus (Caryophyllaceae) was assessed using 15–20 plants from each of 20 natural populations from the southernmost region of Sweden. The stamen fertility data set consisted of 10 characters describing the degree of fertility of the ten stamens/staminoids, while the sepal/gynoecium data set comprised 10 sepal characters, together with style and stigma length. Substantial variation was found in both the degree of development and the fertility of the stamens, the degree of variability in stamen fertility being related to stamen position within the flower. Considerable variation was found in the characters of the sepal and the gynoecium. Hierarchical analyses of variance indicated that 29% of the variation in total male reproductive effort was distributed among populations, 28% among plants within populations and 43% represented within-plant variation. The corresponding averages for the characters from the sepal/gynoecium data set are 26, 38, and 35%: a greater proportion of the total variance in female reproductive characters is accounted for by among individual variation than is the case with the male reproductive characters. Significance tests of Mahalanobis distances derived by canonical variate analyses indicated that all populations were significantly separated using the sepal/gynoecium data set, while only 50% of the pairwise comparisons on the basis of the stamen fertility data set were significant. Cluster analysis did not reveal any aggregation of the populations. The incongruence of the two data sets and their ability to discriminate between the populations is discussed.     

The effect of crossing distances and population subdivision on floral morphology inScleranthus annuus (Caryophyllaceae), a selfing annual

I used a discontinuous population ofScleranthus annuus (Caryophyllaceae) to study the effect of crossing distances on flower morphology of the progeny. Four types of progeny were produced by artificial selfing, crossing with pollen-donors from the same patch in the population, crossing with pollen from donors from other patches in the population and inter-population crosses. The size of gynoecium parts and 12 sepal characters in this petal-lacking species were significantly influenced by the type of cross and the patch in the population from where the seed-parents originated. All comparisons of progeny types except selfed vs progeny produced by within-patch crosses were significantly separated from each other, while all four seed-parent patches used were significantly separated in a multidimensional space.     

Observations on pollination inSarcostemma (Asclepiadaceae)

Field observations on pollination in New World species of the genusSarcostemma R. Br. sensuHolm are reported. Morphological and anatomical comparisons of pollinated flowers ofSarcostemma subg.Ceramanthus Kuntze (New World) andSarcostemma subg.Sarcostemma (Old World) are presented.     

Floral development in Adonideae (Ranunculaceae)

Floral development and floral phyllotaxis in species of Adonis, Callianthemum, and Trollius (Ranunculaceae) were studied with scanning electron microscopy. The floral organs are initiated in spiral sequence and the flowers have spiral phyllotaxis. The sepal primordia are broad, crescent-shaped, and truncate, but those of petals, stamens, and carpels are rather hemispherical. A relatively long plastochron appears to be present between the last sepal and the first petal as compared with the short and equal plastochrones of all subsequent floral organs. Maturation of the stamens within the androecium appears to be centripetal. The carpels have a short ascidiate zone. Placentation is uniformly lateral, even in Adonis and Callianthemum, which have only one fertile ovule per carpel (versus median in other genera of Ranunculoideae with a single fertile ovule). In Adonis and Callianthemum at the tip of the carpel the ventral slit is gaping and the stigma is broadly exposed, whereas in Trollius the stigma is narrower and more pronouncedly decurrent along the ventral slit. The petals in Callianthemum and Trollius are more conspicuously delayed in development than those in Adonis as compared with sepals and stamens. A short carpel stipe is formed early in Callianthemum but later in Adonis and Trollius. In Trollius farreri (commonly having only five carpels in contrast to other species of Trollius) the carpels form a single (spiral) series. Thus floral development is similar in all three genera and, at a lower level, Adonis and Callianthemum are especially close but have different autapomorphies, which reflects the current classification of the genera.     

Floral anatomy ofHypseocharis (Oxalidaceae) with a discussion on its systematic position

The floral anatomy of threeHypseocharis spp. has been studied. The genus resemblesOxalidaceae as well asMonsonia andSarcocaulon of theGeraniaceae. As it is closer toGeraniaceae than toOxalidaceae, it perhaps serves as a connecting link between them.     

Floral morphology and phylogenetic analysis inCrossostylis (Rhizophoraceae)

Floral morphology in all ten species ofCrossostylis, one of the inland genera of Rhizophoraceae and is distributed in the South Pacific Islands, was studied to increase our knowledge on floral features of individual species as well as on relationships among the species. Flowers ofCrossostylis, unlike those of the other Rhizophoraceae, always have semi-inferior ovaries and entire petals, but are diversified concerning the number and arrangement of stamens and carpels, the presence or absence of staminodia, sexuality and the structure of nectaries. Despite some doubt of the presence of apomorphies restricted to the whole genus, we tentatively definedCrossostylis by a combination of the presence of the semi-inferior ovary, entire petals, and arillate seeds, and then performed cladistic analysis on the basis of 24 floral and other morphological characters and withCarallia andGynotroches as outgroups. Our phylogenetic analysis suggested that the species ofCrossostylis are divided into two monophyletic groups: one comprising six species distributed in the Solomon Islands, Vanuatu and the Fiji Islands, and the other comprising four species distributed in New Caledonia and Polynesia.