Carpel Wall Research Articles

Cotton Fiber Length Is Affected by Far‐Red Light Impinging on Developing Bolls

Cotton (Gossypium hirsutum L.) fiber length is an important component of quality as defined by the textile industry. The fibers are single elongated cells that extend from the seed coat during development within bolls. It was hypothesized that elongating cotton fibers would be responsive to the far‐red (FR) to red light (R) photon ratio (FR/R) reflected to developing bolls. To test the hypothesis, plants were grown in trickle irrigated field plots over different colored soil covers that reflected high FR/R and low photosynthetic photon flux (PPF), or low FR/R and high PPF to developing bolls. Newly opened flowers were tagged over three replicate plots of each of four colors. After the flowers were fertilized, randomly selected young bolls were covered with aluminum foil to shield them from light during development. Others served as unshielded controls. The FR/R and PPF impinging on developing bolls affected biomass per area of carpel walls and the amount of FR transmitted into the bolls to the developing fibers. Fiber lengths were determined after the bolls matured. Fibers in unshielded bolls that developed over green and red (higher reflected FR/R) soil covers were significantly longer than those that developed over aluminum and white (higher reflected PPF). The difference in length of fiber developed in unshielded versus shielded bolls was greater over green and red than over aluminum and white indicating a greater response to increased FR/R than to increased PPF impinging on the developing bolls. These results suggest that reflected FR should be considered along with other environmental factors when developing innovative production systems that involve nontraditional row spacing, plant population densities, or soil surface conditions that can affect the photon ratios to which the developing plants are exposed.

CRABS CLAW and SPATULA, two Arabidopsis genes that control carpel development in parallel with AGAMOUS.

To help understand the process of carpel morphogenesis, the roles of three carpel development genes have been partitioned genetically. Mutants of CRABS CLAW cause the gynoecium to develop into a wider but shorter structure, and the two carpels are unfused at the apex. Mutants of a second gene, SPATULA, show reduced growth of the style, stigma, and septum, and the transmitting tract is absent. Double mutants of crabs claw and spatula with homeotic mutants that develop ectopic carpels demonstrate that CRABS CLAW and SPATULA are necessary for, and inseparable from, carpel development, and that their action is negatively regulated by A and B organ identity genes. The third carpel gene studied, AGAMOUS, encodes C function that has been proposed to fully specify carpel identity. When AGAMOUS function is removed together with the A class gene APETALA2, however, the organs retain many carpelloid properties, suggesting that other genes are also involved. We show here that further mutant disruption of both CRABS CLAW and SPATULA function removes remaining carpelloid properties, revealing that the three genes together are necessary to generate the mature gynoecium. In particular, AGAMOUS is required to specify the identity of the carpel wall and to promote the stylar outgrowth at the apex, CRABS CLAW suppresses radial growth of the developing gynoecium but promotes its longitudinal growth, and SPATULA supports development of the carpel margins and tissues derived from them. The three genes mostly act independently, although there is genetic evidence that CRABS CLAW enhances AGAMOUS and SPATULA function.

Genetic pathways controlling carpel development inArabidopsis thaliana

Carpel development inArabidopsis is known to be controlled by the organ identity geneAGAMOUS. However, even in the absence of AGAMOUS function, many carpel properties can arise suggesting that other genes are also involved. Two new carpel genes,CRABS CLAW andSPATULA, have been recognised by their specific disruptions to carpel development in mutant plants. These disruptions suggest thatCRABS CLAW normally plays a role in promoting the growth of specific regions of the carpel wall, whereasSPATULA apparently has a primary function in promoting development of the transmitting tract. When the function of these genes is also compromised along with that ofAGAMOUS in multiply mutant plants, carpelloid properties vanish. ThusAGAMOUS, CRABS CLAW andSPATULA act together in specifying carpel development, although none can do this alone. BecauseSPATULA mutants are epistatic to mutants of another carpel development gene,ETTIN, the latter may normally act by suppressing the action ofSPATULA in specific regions of the developing gynoecium. There is indirect evidence thatETTIN, and another morphogenetic gene,PINOID, act through regulating auxin-induced growth in specific regions of the developing flower, but it is not yet known how this could result in the suppression of SPATULA function.

Stigma development in Nicotiana tabacum. Cell death in transgenic plants as a marker to follow cell fate at high resolution

Pistil development was studied in transgenic tobacco plants in which the stigma is ablated by expression of a stigma-specific cytotoxic gene. These plants offer a tool to investigate the process of differentiation of the secretory zone, in that cell death caused by barnase activity provides a marker to follow cell fate at high resolution. After fusion of the carpel walls in the region most distal from the ovary, the epidermal cells begin to divide in both wild-type and stigmaless plants. Divisions of the L1 layer of the pistil are immediately followed by the morphogenetic events that lead to three different cell types: rounded-angular cells showing an equal number of anti- and periclinal divisions, cells that are more oblong forming the transition zone, and the square cells of the transmitting tissue dividing mostly anticlinally with respect to the original carpel wall. In the stigmaless plants, cell death caused by the expression ofSTIG 1-barnase begins at stage −1 and proceeds gradually, but is always associated with round epidermal cells and with angular-rounded cells underneath them. Studies at the ultrastructural level show that cell death caused by barnase activity occurs first in solitary cells and gradually extends to groups of cells.In situ hybridizations using the STIG 1 RNA probe in wild-type pistils confirm these results. Most likely, the cells in whichSTIG 1 is expressed are those that have just differentiated into the secretory cell type. Our results indicate that the transition zone or neck is autonomously differentiated from the secretory zone and the transmitting tissue. Furthermore, our results indicate that in both wild-type and stigmaless pistils secretion of lipids most likely occurs through the plasmodesmata. This observation suggests that bulk transport can occur via plasmodesmata.

Stigma development in Nicotiana tabacum. Cell death in transgenic plants as a marker to follow cell fate at high resolution

Pistil development was studied in transgenic tobacco plants in which the stigma is ablated by expression of a stigma-specific cytotoxic gene. These plants offer a tool to investigate the process of differentiation of the secretory zone, in that cell death caused by barnase activity provides a marker to follow cell fate at high resolution. After fusion of the carpel walls in the region most distal from the ovary, the epidermal cells begin to divide in both wild-type and stigmaless plants. Divisions of the L1 layer of the pistil are immediately followed by the morphogenetic events that lead to three different cell types: rounded-angular cells showing an equal number of anti- and periclinal divisions, cells that are more oblong forming the transition zone, and the square cells of the transmitting tissue dividing mostly anticlinally with respect to the original carpel wall. In the stigmaless plants, cell death caused by the expression ofSTIG 1-barnase begins at stage −1 and proceeds gradually, but is always associated with round epidermal cells and with angular-rounded cells underneath them. Studies at the ultrastructural level show that cell death caused by barnase activity occurs first in solitary cells and gradually extends to groups of cells.In situ hybridizations using the STIG 1 RNA probe in wild-type pistils confirm these results. Most likely, the cells in whichSTIG 1 is expressed are those that have just differentiated into the secretory cell type. Our results indicate that the transition zone or neck is autonomously differentiated from the secretory zone and the transmitting tissue. Furthermore, our results indicate that in both wild-type and stigmaless pistils secretion of lipids most likely occurs through the plasmodesmata. This observation suggests that bulk transport can occur via plasmodesmata.

The Brassica napus extA extensin gene is expressed in regions of the plant subject to tensile stresses

The expression of extA, an extensin gene from Brassica napus L. (oilseed rape) was examined in transgenic Nicotiana tabacum L. (tobacco) and untransformed Brassica juncea L. and B. napus tissues. Northern analysis showed that this gene maintained its normal pattern of expression when transferred to tobacco. In transgenic tobacco plants containing an extA promoter/β-glucuronidase coding sequence fusion, expression of extA was detected in the external and internal phloem of the main stem. High expression levels were seen in cortical parenchyma cells at the point where the axillary flowering branch joined the main stem. Expression was greatest in regions where the maximum tensile stress would seem to be exerted on the main stem by the weight of the axillary branch. It was confirmed that this expression pattern was due to tensile stress by using weights to induce expression of the fusion gene in axillary flowering stalks. In B. juncea pods, in-situ hybridisation studies showed that the extensin gene was strongly expressed in cells of the carpel walls within which considerable tensile stresses develop.

Comparisons between an Upland and a Pima Cotton Cultivar: II. Nutrient Uptake and Partitioning

AbstractUptake and partitioning of N, P, and K by Upland cotton (Gossypium hirsutum L.) have been studied, but no such work has included American Pima cotton (G. barbadense L.). Our objective was to describe the N, P, and K uptake and partitioning into various plant parts for two representative Upland and Pima cotton cultivars. Upland ‘Deltapine 90’ (DPL 90) and Pima ‘S‐6’ were grown at two south‐central Arizona locations for 3 yr. Beginning 14 to 20 d after emergence, the aboveground portions of cotton plants were harvested and separated into stems, leaves (including petioles), burs (carpel walls), lint, and seeds. The bur fraction also included squares, flowers, immature bolls, and burs from mature bolls. Total N, P, and K analyses were conducted on each fraction (except lint). Nutrient concentration, uptake, and partitioning by cotton was modeled on a heat unit accumulation basis (HUAP). Up to about 1500 HUAP, leaves were major N sinks, leaves and the bur fraction were major P sinks, and leaves and stems were major K sinks for both cultivars. After 1500 HUAP, the bur fraction and seeds were major N and P sinks and the bur fraction was the major K sink. For DPL 90, the total N, P, and K uptake was 201, 31, and 254 kg ha−1 and for Pima S‐6, it was 201, 32, and 226 kg ha−1, respectively. Nutrient requirements for producing 100 kg lint ha−1 were 15‐2.3‐19 kg ha−1 N‐P‐K for Upland cotton and 21‐3.3‐23 kg ha−1 for Pima cotton.

Comparisons between an Upland and a Pima Cotton Cultivar: I. Growth and Yield

AbstractAmerican Pima cotton (Gossypium barbadense L.) is an extra‐long staple cotton produced in the southwestern USA and in other regions around the world. Pima cotton generally yields less than Upland (G. hirsutum L.), but there have not been any studies conducted to document the basis for these differences. Field trials were conducted at two south‐central Arizona locations from 1990 through 1992 for the purpose of comparing growth and yield between representative cultivars of Upland and Pima cotton. The aboveground portion of Upland ‘Deltapine 90’ (DPL 90) and Pima ‘S‐6’ were harvested and separated into stems, leaves (including petioles), burs (carpel walls), lint, and seeds. The bur fraction also included immature fruiting forms. Dry matter accumulation was modeled as a function of heat units (HU) accumulated after planting (HUAP). Both cultivars exhibited a linear increase of total dry matter over the duration of sampling. By the end of sampling, DPL 90 produced more total, stem, seed, lint, and reproductive (bur + seed + lint) dry matter than Pima S‐6; the dry matter that accumulated in leaves, bur fraction, and vegetative structures (leaf + stem) did not differ. The reproductive/vegetative ratio (RVR) was found to be similar for both cultivars, increasing rapidly with HU accumulation. Comparisons of lint dry matter accumulation as a function of RVR and harvest index (HI) revealed that DPL 90 yields more lint than Pima S‐6 due to a greater total biomass production and more efficient partitioning of dry matter into reproductive organs.

The floral development and floral anatomy ofCoris monspeliensis

The floral development of Coris was investigated to clarify its controversial relationship with either Primulaceae (Primulales) or Lythraceae (Myrtales). We demonstrate that Coris is strongly related to the Primulaceae but differs in a few important features, such as the presence of an epicalyx and partial zygomorphy. The saccate calyx and epicalyx with unilateral development encloses an actinomorphic flower. The stamen–petal tube has two sections that arise through three growth processes: a lower common part for stamens and petals and an upper section representing a fused corolla. The central ovule-bearing part of the ovary arises separated from the carpel wall. The formation of ridges with teethlike appendages between the ovules suggests a derivation of the free-central placentation from an axile arrangement. Several characters support the monotypic family Coridaceae near the Primulaceae. Key words: Coridaceae, Primulaceae, Lythraceae, floral development, floral vasculature, epicalyx, free-central placentation, common primordium, zygomorphy.

Improvements for observing Anthurium (Araceae) floral structures by light microscopy.

Three major obstacles must be overcome in the anatomical study of Anthurium floral structure and embryo development including presence of mucilage, hardened carpel walls, and hardened seed coat in the developing fruit and seed. Fixation in 6% glutaraldehyde and 1% cetylpyridinium chloride in 0.05 M sodium cacodylate, pH 6.8, effectively fixed or removed mucilage from the locules of Anthurium andraeanum Hort. in spadices. This treatment enhanced infiltration of the embedding medium through the hardened carpel wall into the locule space and decreased the quantity and size of holes in the embedding block during sectioning. Specimens 16 weeks after pollination could be fixed, infiltrated, and observed without physical removal of the seed coat. Embryos may be excised from the seed at later stages without compromising embryo structure.

Seed ontogeny in Adesmia securigerifolia (Fabaceae‐Adesmieae)

A study of the reproductive processes of Adesmia securigerifolia from bud to mature seed was carried out by means of field observations and the paraffin technique. Observations revealed the following new contributions to the study of legume embryology: 1) after fertilization, a small nucellar haustorium, or micropylar nucellar beak, was observed for the first time, originating from two obliterating nucellar cells that extended outwards. Their globose distal end comes in contact with the internal carpel wall, while the wedge shaped base stretches into the micropyle; a suspensor consisting of five or more cells ‐ the two basal cells are large and falcate and fit into the micropylar pore ‐ coexists with the undivided polar nuclei thus showing that endosperm formation begins after zygote division; 2) at the young embryo stage, a sac‐ shaped nuclear haustorium, formed by the endosperm, adjoins the outer integument and is not connected to the chalaza, or any vascular element; at the hilar level, a nucellar projection is formed in connection with the haustorial coenocytic endosperm. This projection persists up to the mature seed stage when it starts to degenerate, after performing another linking with the embryo nutrition system; 3) at the mature seed stage, the seed coat evolving from the outer integument has a single macrosclereid layer, though inclusions in the cell vacuoles simulate the presence of more layers and/or transverse walls. The lens, a hypodermal layer of osteosclereids (hour‐glass cells), and the astrosclereids are also described.

Comparative anatomy and systematics of woody Saxifragaceae. Aphanopetalum Endl.

The floral and vegetative anatomy of the small Australian genus Aphanopetalum were studied. Wood is described for the first time and is characterized by predominantly solitary pores, scalariform vessel element perforation plates with low bar numbers, imperforate tracheary elements with distinctly bordered pits, sparse axial parenchyma, and a combination of homocellular and heterocellular rays. Starch occurs in both axial and ray parenchyma of the wood. Stems possess unilacunar, one-trace nodes and the uncommon feature of an endodermis with well-defined Casparian strips. Leaves have anomocytic stomata, a bifacial mesophyll and semicraspedodromous venation or a combination of semicraspedodromous and brochidodromous venation. The tetramerous flowers are apetalous or have minute petals. The compound, half-inferior gynoecium consists of essentially totally united carpels. The pattern of floral vascularization resembles different Saxifragaceae sensu lato in that the compound sepal-plane and petal-plane traces give rise to staman bundles as well as sepal, petal, and carpel wall venation in their respective planes. The ventral ovarian bundles are fused into a single ventral complex that subdivides at the top of the ovary to form ventral bundles and to supply the one ovule in each locule. Vegetative and floral features provide compelling evidence to suggest that Aphanopetalum has its nearest relatives among the Saxifragaceae sensu lato rather than Cunoniaceae. The genus is probably best treated as forming its own subfamily (or family) among the saxifragaean alliance.

Comparative anatomy and systematics of woody Saxifragaceae. Aphanopetalum Endl.

Abstract The floral and vegetative anatomy of the small Australian genus Aphanopetalum were studied. Wood is described for the first time and is characterized by predominantly solitary pores, scalariform vessel element perforation plates with low bar numbers, imperforate tracheary elements with distinctly bordered pits, sparse axial parenchyma, and a combination of homocellular and heterocellular rays. Starch occurs in both axial and ray parenchyma of the wood. Stems possess unilacunar, one-trace nodes and the uncommon feature of an endodermis with well-defined Casparian strips. Leaves have anomocytic stomata, a bifacial mesophyll and semicraspedodromous venation or a combination of semicraspedodromous and brochidodromous venation. The tetramerous flowers are apetalous or have minute petals. The compound, half-inferior gynoecium consists of essentially totally united carpels. The pattern of floral vascularization resembles different Saxifragaceae sensu lato in that the compound sepal-plane and petal-plane traces give rise to staman bundles as well as sepal, petal, and carpel wall venation in their respective planes. The ventral ovarian bundles are fused into a single ventral complex that subdivides at the top of the ovary to form ventral bundles and to supply the one ovule in each locule. Vegetative and floral features provide compelling evidence to suggest that Aphanopetalum has its nearest relatives among the Saxifragaceae sensu lato rather than Cunoniaceae. The genus is probably best treated as forming its own subfamily (or family) among the saxifragaean alliance.

New Evidence Relating the Pilose Allele and Micronaire Reading in Cotton

Experiments were undertaken to determine whether close linkage between the pilose allele and a locus influencing cotton (Gossypium hirsutum L.) fiber fineness had been misinterpreted as pleiotropy. Pilose (T1), the dominant allele to the t1 locus, is phenotypically described by a high density of trichomes on the leaf surface, the presence of trichomes on the carpel wall, and increased micronaire. Two lines, 239‐17/6 and 250‐14/2, were derived from single plant selections of pilose plants in an ‘Empire’ genetic background. 239‐17/6 has atypically low micronaire readings. The 239‐17/6 line was crossed to 250‐ 14/2, a pilose, high‐micronaire line, and to lines carrying t1 (normally pubescent) and Tsm1 (glabrous). The F1 plants were selfed for F2 and backcrossefl to t1 and Tsm1 parents. Similar hybrids and backcrosses were made between 250‐14/2 and t1 locus recessives. The agronomic performance and fiber traits of 239‐17/6, 250‐14/2, Empire, and FTA (low micronaire check) were measured for 2 yr in replicated experiments. Lint yield, lint percent, and the fiber traits of elongation, maturity, micronaire, perimeter, span length, strength, and wall thickness were measured. 239‐17/6 expressed a T1 pilose phenotype. All 465 F2 seedlings from 239‐17/6 × 250‐14/2 and reciprocal cross had tomentose leaves. The combined results from crosses of 239‐17/ 6 and 250‐14/2 with t1 and Tsm1, and backcrosses of F1 to t1 and Tsm1 demonstrated that 239‐17/6 and 250‐14/2 both carry T1. The fiber of 239‐17/6 was not distinguishable from the fiber of either Empire or FTA for the wall traits of maturity, micronaire, and wall thickness. 239‐17/6 was shown to have the T1 phenotype and behave genetically like T1. Since T1 was associated with both high and low micronaire readings, the pleiotropic effect of T1 on micronaire appears unlikely. A more likely explanation is the T1 is linked to a gene or block of genes that influence micronaire.

PISTIL DEVELOPMENT AND PARIETAL PLACENTATION IN THE PSEUDOMONOMEROUS OVARY OF ZELKOVA SERRATA (ULMACEAE)

Development of female flowers in Zelkova serrata was observed using epi‐illuminated microscopy and scanning electron microscopy, with particular attention given to placentation. After the inception of staminodial primordia, the floral apex becomes flat, and the first and subsequently the second carpel primordia appear at opposite comers of the pistil primordium. Inside each carpel primordium a fossette forms. Through differential growth this depression becomes clear and the carpel wall encircles one side of the future placental region. The placental region is detectable even in early stages, but clear signs of ovule inception appear late when the placental region is elevated onto one side of the ovary wall by intercalary growth. Although the relative size of the two carpels varies among flowers, the placental position always appears to be the border between the two carpels and the floral apex. This suggests that the placentation of Zelkova is parietal. The ovule position in tricarpellate ovaries also suggests an evolutionary derivation from ovaries with parietal placentation. Parietal placentation appears to be the original condition in Urticales.

Pistil Development and Parietal Placentation in the Pseudomonomerous Ovary of Zelkova serrata (Ulmaceae)

Development of female flowers in Zelkova serrata was observed using epi-illuminated microscopy and scanning electron microscopy, with particular attention given to placentation. After the inception of staminodial primordia, the floral apex becomes flat, and the first and subsequently the second carpel primordia appear at opposite comers of the pistil primordium. Inside each carpel primordium a fossette forms. Through differential growth this depression becomes clear and the carpel wall encircles one side of the future placental region. The placental region is detectable even in early stages, but clear signs of ovule inception appear late when the placental region is elevated onto one side of the ovary wall by intercalary growth. Although the relative size of the two carpels varies among flowers, the placental position always appears to be the border between the two carpels and the floral apex. This suggests that the placentation of Zelkova is parietal. The ovule position in tricarpellate ovaries also suggests an evolutionary derivation from ovaries with parietal placentation. Parietal placentation appears to be the original condition in Urticales.

A flower-specific cDNA encoding a novel thionin in tobacco.

We isolated a flower-specific cDNA, FST (flower-specific thionin), which encodes a novel thionin from tobacco. Thionins are basic and cysteine (Cys)-rich, low molecular weight proteins found in many plants. They are believed to play a role in plant defense against pathogens. The central domain of the FST protein shares homology with three gamma-thionins. Like other thionin precursors, the FST protein has an N-terminal domain characteristic of a signal peptide and an acidic C-terminal domain. FST mRNA accumulates specifically in developing flowers and its level drops as flowers mature. Transcripts are present in petals, stamens and pistil but are not detectable in sepals. In situ hybridization revealed that FST mRNA is most abundant in the epidermal cells along the adaxial surface of petals, and in the surface cell layers of the carpel and anther walls. If the FST protein indeed has a protective role in flowers, this pattern of spatial distribution of FST mRNA would appear to maximize this effect on the two internal reproductive whorls. A possible biological role for FST is discussed.

Ultrastructural Studies on the Ontogeny of Grapefruit Juice Vesicles (Citrus paradisi Macf. CV Star Ruby)

The ultrastructure of juice vesicle development and maturation was investigated in cv Star Ruby grapefruit. Juice vesicle primordia were initiated by divisions of epidermal and subepidermal cells on the adaxial surface of the carpel wall at least 2 d before anthesis. Development occurred in three distinct stages: cell division, cell elongation, and cell maturation. Development of juice vesicles in the first 3 wk postanthesis occurred by cell division of a subterminal meristem and resulted in the formation of a main juice vesicle body subtended by highly vacuolate stalk cells connected to the carpel wall. Cells of the main body were characteristic of meristematic cells. Between 4 and 10 wk postanthesis, oil gland/oil cavity development occurred in the center of the main juice vesicle body and began with a single electron-dense cell. Surrounding cells exhibited characteristics of intense metabolic and secretory activity, culminating in the synthesis of lipid and osmiophilic material. A schizogenous and/or l...

Optical properties of the pod wall of the pea ( Pisum sativum L.): I general aspects

Summary The %transmission, reflection and absorption of the carpel wall of Pisum sativum L. has been compared with other pea tissues: leaf, testa and cotyledon. Although considerable overall differences were found, especially in the levels of light that were transmitted, there were qualitative similarities which correlated with the presence of chlorophyll in all the tissues. Reasonably high maximum light fluxes were found within the green pod and testa of Pisum sativum L. exposed to sunlight but these would be considerably lower under canopy conditions. The presence or absence of wax on the pod surface did not affect transmission, reflection or absorption spectra significantly. The sclerenchyma layer made a significant contribution to pod reflection, and to the absorption of potentially harmful near-UV radiation, while the inner layer of cells had a high absorption of red and blue wavelengths consistent with chlorophyll absorption. The chlorophyll concentrations were found to be highest in the inner layer and cotyledon tissues, but still much lower than those in leaves. The Red/Far-Red ratio decreased as light penetrated the pod and testa, so that the photomorphogenic environment of the embryo had a much lower R/FR ratio than that of daylight. This may have implications for seed development. The optical properties of pods are discussed in relation to their photosynthetic function and possible photomorphogenic consequences for the developing seeds within the modified light regime of the pod.

An Additional Note on the Floral Morphology and Affinities of Medusagyne Oppositifolia (Medusagynaceae)

Further observations on the floral morphology and anatomy of the monotypic genusMedusagyne from the Seychelles are presented. The unique synovarious gynoecium is composed of numerous carpels that are attached to the side of a broad, elongated torus. The biovulate carpels are differentiated into a narrow ovary, a stout, erect, three-trace style, and a lobed, discoid stigma. The carpel wall is initially composed of thin-walled parenchyma, but at later stages of development the peripheral region becomes subdivided into many lignified sterile extensions. Carples show pronounced ontogenetic adaxial deformation, during which the upper ventral surfaces become expanded, greatly extending the ventral margins and forming a domelike cushion of carpel-derived tissue over the summit of the torus. The distal cushion remains separated from the flattened torus by a compressed cavity and eventually undergoes lignification, perhaps protecting the underlying gynoecium from chewing insects and exposure. Comparisons are made between the mature gynoecia ofMedusagyne and those of the genusDillenia. The occurrence of S-type sieve-element plastids inMedusagyne is reported for the first time, a feature in agreement with suggested thealean affinities of the family.