Floral venation patterns in Siphocampylus (Campanulaceae)

Siphocampylus is a neotropical genus that comprises 221 species distributed from Costa Rica to Argentina and in the Greater Antilles. Twenty-eight species have been reported from Brazil, mainly occupying mountainous terrain. The floral venation patterns and the origin of the hypanthium in eight Brazilian species, including three varieties, are described. Eleven ovarian vascular bundles depart from the siphonostele or receptacular stele: five of these bundles result from sepalar and staminal adnation and are alternate to five petalar bundles; the remaining bundle is central carpellary. The staminal bundles diverge from the sepalar bundles at the sinus, while the carpellary bundles form a cross, resulting in four ventral bundles; two of these feed the ovules; the other two feed the style. Apparently, the dorsal carpellary bundles diverge at the same site and then ramify profusely. The venation pattern observed is unprecedented in Siphocampylus and is quite different from other reports on genera of Campanulaceae. Further, these findings suggest that the origin of the hypanthium is appendicular, increasing knowledge of venation in this group, thus providing data for phylogenetic considerations.     

STUDIES ON THE FLORAL ANATOMY OF THE CUNONIACEAE

Twenty-two genera representing sixty-two species of Cunoniaceae and Davidsonia were examined with respect to floral anatomy. Sepals are vascularized by three traces with the lateral traces of adjacent sepals united. Pancheria is unique for the family with species in which the sepals are vascularized by a single, undivided bundle. Petals, when present, and stamens, are uniformly one-trace structures. A general tendency exists within the family for the principal floral bundles to unite in various ways, with fusions evident between calyx, corolla, and androecial vascular supplies. Carpel number ranges from two to five and the gynoecium is generally surrounded by a prominent disc. Gynoecia of Ceratopetalum and Pullea are “half-inferior.” The number of ovules per carpel locule ranges from one to numerous. Ventral carpel sutures range from open to completely sealed at the level of placentation. Carpels of the apocarpous genus Spiraeanthemum (incl. Acsmithia) are vascularized by a dorsal bundle and either three or four bundles constituting the ovular and wing vasculation in the ventral position, a condition unlike other members of the family. Ovules are supplied by the median ventral bundle. More advanced bicarpellate gynoecia within the family are predominately vascularized by a dorsal and two ventral bundles although a variable number of additional lateral wall traces may be present. A major trend exists toward fusion of the ventral bundles of adjacent carpels in the ovary of both bicarpellate and multicarpellate plants. At the base of the styles the fused ventral strands separate and extend along with the dorsal carpellary bundles into styles of adjacent carpels. In Pullea the ventral bundles terminate within the ovules. The united ventral carpellary bundles in Aphanopetalum, Gillbeea, and Aistopetalum lie in the plane of the septa separating adjacent carpels. Ovules are vascularized by traces originating from the vascular cylinder at the base of the gynoecium or by traces branching from the ventral bundles. Ovular traces in each carpel are united, or remain as discrete bundles, prior to entering the placenta. Tannin and druses are common throughout all floral parts. Although floral anatomy generally supports the position of Cunoniaceae near Saxifragaceae and Davidsoniaceae, the evolutionary relationship of the Cunoniaceae to the Dilleniaceae is uncertain.     

THE PALM GYNOECIUM

The morphology, anatomy, and histology of the gynoecia at or close to anthesis are described for 20 genera of palms selected to represent different taxonomic alliances and to include major gynoecial types within the family. Palms may have 1–10 carpels, but most have three. Fifteen genera, including 14 coryphoid palms and the monotypic Nypa fruticans, are apocarpous and the remainder, approximately 190, are syncarpous. Fusion of carpels in some gynoecia begins in the base, in others in the styles. Pseudomonomerous pistils occur in several different alliances: the ovarian parts of two carpels are reduced but three usually equal and functional styles and stigmas are present. The carpel is often follicular in shape with the ventral suture open or, more frequently, partially or completely closed. The carpel may be stipitate or sessile and usually has a conduplicate laminar part. Most carpels are spirally and laterally inserted on the receptacle, but the carpel in some unicarpellate genera (e.g., Thrinax) appears terminal. Stipes, ovarian parts, styles, and stigmas vary in structure and development. Septal nectaries which differ in size, in the presence or absence of specialized canals, and in position, characterize all genera of some groups but only some genera of others. Diverse vascular configurations in the bases of gynoecia vary according to the extent of the floral axis, the development of carpellary stipes, and the connation of the carpels and their adnation to the tip of the floral axis. Four types of carpellary vascular systems are present in the genera described: (1) most palm carpels have three major traces consisting of a dorsal bundle and two ventral bundles, and they may also have up to four pairs of lateral bundles or occasionally more; (2) in certain cocosoid palms no ventral bundles can be distinguished, but a dorsal bundle, many parallel lateral bundles, and a row of immature ventral strands vascularize each carpel; (3) carpels of Phytelephas have a dorsal bundle, two pairs of major lateral bundles and about four pairs of shorter lateral bundles, with no identifiable ventral bundles; (4) carpels of Nypa have many dichotomously branched bundles but none that are recognizable as dorsal, ventral, or lateral strands. Additional peripheral bundles or systems may be present in each of the above types. Ovules are supplied by 1–15 bundles. These are derived either from the carpellary stele; from ventral bundles only; from ventral, lateral, and dorsal bundles; or from a combination of these origins. Certain areas of the gynoecia or certain parts of dorsal carpellary walls in some genera are much less mature at anthesis than surrounding tissues. Implications for floral biology and relationships within the palms and of palms to other groups are discussed.     

Comparative morphology of the carpel in the Liliaceae: Colchiceae (Androcymbium)

The pistil of Androcymbium closely resembles that of Colchicum : it is tricarpellate usually, syncarpous and multiovulate, and the carpels of most species have open sutures and bitegmic ovules. The only species with closed carpellary sutures, A. dregei has monotegmic ovules. There are always three dorsal bundles and three compound septal bundles, which latter may bifurcate into simple septal bundles. Six placental bundles (two per carpel) are differentiated, either separately from the compound septal bundles or as lateral branches of them. A statistical evaluation of 47 species (6 genera) of the hemisyncarpous Wurmbaeoideae shows a significant tendency for bitegmic ovules and two simple septal bundles per septum to be associated with open sutures and for monotegmic ovules and no septal bundles to be associated with closed sutures.     

COMPARATIVE STUDY OF THE FLORAL VASCULATURE IN SAURURACEAE

The floral vascular systems are compared among all six taxa of Saururaceae, including the two species of Gymnotheca which have not been studied previously. All are zygomorphic (dorsiventrally symmetrical), not radial as sometimes reported, in conformity with dorsiventral symmetry during organogenesis. Apocarpy in the two species of Saururus (with four carpels and six free stamens) is accompanied by a vascular system of four sympodia, each of which supplies a dorsal carpellary bundle, two ventral carpellary bundles, and one or two stamen traces. The level at which the ventral bundles diverge is the major difference in vasculature between the two species. The other four taxa are all syncarpous, and share some degree of stamen adnation and/or connation. The vascular systems also show varying degrees of fusion. The two species of Gymnotheca (with four carpels and six stamens) are very similar to each other; in both, the ventral traces of adjacent carpels fuse to form a placental bundle, which supplies the ovules and then splits into a pair of ventral strands. The flowers of Houttuynia cordata (with only three carpels and three adnate stamens) are sessile. Each flower is vascularized by three sympodia; the median adaxial sympodium is longer than the other two sympodia before it diverges to supply the adaxial organs. Three placental bundles also are formed in Houttuynia, but the three bundles differ in their origin. The median abaxial placental bundle diverges at the same level as the three sympodial bundles of the flower, while the other two lateral placental bundles diverge at a higher level from the median adaxial sympodium. Anemopsis californica, with an inferior ovary of three carpels, sunken in the inflorescence axis, and six stamens adnate to the carpels, has a vascular system very similar to that of Houttuynia cordata. The modular theory of floral evolution is criticized, on the bases of the known behavior of apical meristems and properties of vascular systems. The hypothesis is supported that saururaceous plants may represent a line of angiosperms which diverged very early.     

ANATOMY OF THE GYNOECIUM IN TWO SPECIES OF BAKERIDESIA (MALVACEAE)

Structure of the gynoecium is described in two species of Bakeridesia, subgenus Bakeridesia (Malvaceae, tribe Malveae). The dorsal wall of each carpel bears a winglike projection with a marginal pair of pubescent, bluntly dentate wings. The projection arises as a single, solid ridge of tissue after the ovules are initiated and after the ventral carpellary margins are fused with the receptacle. Two multiseriate layers of fiber-sclereids line each locule and continue into the winglike projection where they are separated by parenchyma. Gynoecial vascularization is described in detail. The richly vascularized carpels are supplied by five traces: a median dorsal trace, which bifurcates into two dorsal bundles; two lateral traces; and two ventral traces. Adjacent ventral traces, lateral traces, and septal bundles are fused—i.e., they are held in common by neighboring carpels. The presence of lateral carpellary traces may be a primitive character in the tribe Malveae.     

THE AFFINITIES OF PRINSEPIA (ROSACEAE)

Sterling, C. (U. California, Davis.) The affinities of Prinsepia (Rosaceae). Amer. Jour. Bot. 50(7): 693–699. Illus. 1963.—Anatomical study of the carpels of 4 species of Prinsepia has shown that at flowering the 2 ovules are erect and pleurotropic. The funiculus is on the dorsal and lower side of the ovule; the micropyle faces a large obturator on the ventral side. The carpellary margins are separated by a fissure below the funicular insertion, but above this level they are fused. The style is laterally inserted on the ventral face of the carpel; it is vascularized only by the wing bundles and the recurving dorsal bundle. At the base of the ovary, 2 ovular bundles depart from the vascular cylinder and run separately, each to its respective ovule. In carpel morphology, ovular position, ovule structure, and vascular anatomy, Prinsepia is not a prunoid type. Although its features on the whole resemble those of chrysobalanoid plants, there are notable differences. Consequently, Prinsepia is assigned to a new subfamilial group in the Rosaceae, the Prinsepioideae. Some phylogenetic considerations are discussed briefly.     

THE ANATOMY OF THE PISTILLATE INFLORESCENCE AND FLOWER OF CASUARINA VERTICILLATA LAMARCK (CASUARINACEAE)

The pistillate inflorescence of Casuarina verticillata is described as consisting of a primary axis bearing whorls of bracts with a cymule in the axil of each bract of the more central whorls. Each cymule consists of an atepallate, two-carpellate, syncarpous floret and two, lateral, once-lobed bracteoles. A “peripheral intercalary” meristem, in which divisions are primarily periclinal, forms a meshwork beneath the bracts from early development and moves the connate bracts centrifugally around the cymules and extends and binds the bracts, and to some extent the bracteoles, of the fertile part of the inflorescence together. Each bract receives a single trace; each cymule receives two traces. Each bundle extension of a cymule trace supplies: 1) a branch which joins its counterpart to become the anterior common carpellary bundle; 2) a second branch which joins its counterpart to become the posterior common carpellary bundle; and 3) a central branch which supplies a lateral bracteole. Within each floret, each common carpellary bundle provides a dorsal carpellary bundle, two ventral carpellary bundles (fertile anterior carpel) or one common ventral bundle (sterile posterior carpel). The ventral bundle-supplies join and form a single placental bundle which lies in the gynoecial septum, and which, in turn, supplies the two ovules in the anterior carpel. Whether the inflorescence is a simple racemose or a condensed cymose type cannot be determined from this species alone. The function of the sclerenchymatous, enclosing bracteoles and connate bracts is discussed.     

A SURVEY OF FLORAL ANATOMY IN ARACEAE

Flowers of 23 species representing six subfamilies of Araceae were studied by means of serial cross sections, special attention being given to vascular patterns and to taxa of supposed phylogenetic importance. Floral structure is shown to be extremely diverse with no unifying pattern common to all subfamilies. Conclusions include the following: (1) Lysichiton has a specialized gynoecial vascular pattern which differs from others encountered in the survey and which weighs against the primitive position attributed to this genus by Hutchinson. (2) Philodendron, with its multiple stylar canals, cannot have originated from subfamily Pothoideae, as Engler's phylogenetic concept would require of all Araceae; instead, it appears that several syncarpous evolutionary lines have evolved independently from extinct apocarpous members of the family. (3) In Acorus, stamens are introrse and dorsal carpellary bundles are lacking; these characters and others justify the recognition of Acorus as a separate subfamily Acoroideae. In addition, the survey revealed a peculiar deterioration of the inner ovary wall and the septa in several taxa, apparently a normal feature of floral development. Spathiphyllum solomonense Nicolson is described in an appendix.     

Floral vasculature and ontogeny in Canna indica

The identity of the labellum is a hot point in Zingiberales, which has long been discussed by many authors. In this study, floral vasculature and ontogeny of Canna indica (Cannaceae) was observed by LM and SEM in order to ascertain the identity of the labellum and the functional stamen of this species and provide evidence for the homologies of the floral organs in Zingiberales. The results indicate that the labellum of C. indica have incorporated two androecial members from both outer and inner whorls, rather than three, one or half member, as previously suggested by morphologists of Cannaceae flowers. The two labellum traces are here interpreted as: one from the outer androecial whorl (diverging from the carpellary dorsal bundle), while the other from the inner androecial whorl (diverging from the parietal bundle). The functional stamen also incorporates two androecial bundles, the same as the labellum: one trace from the carpellary dorsal bundle, and the other (the petaloid appendage) from the parietal bundle. In addition, the origin of the vascular system in the androecium of Zingiberales and its systematic significance are discussed.     

Biosystematic studies onMaianthemum (Liliaceae-Polygonatae)

A similar floral vascular anatomy involving a constant dimerous, bicarpellate plan for each of the threeMaianthemum species is reported. All of the tepal, stamen and ovary traces are derived via repeated radial division of two pedicel bundles. The four tepal and stamen traces are fusion products, as are the two dorsals. A third, smaller (vestigial) pedicel bundle which continues unbranched and uninvolved into the ovary was observed in all three species. It could indicate a past reduction from a trimerous, tricarpellate condition, and gives a basis for comparison to the closely related genusSmilacina. The gynoecial vasculature lacks peripheral laterals, septal axials and terminal cross-connections between the dorsal and ventral supplies. The placentation is only apparently axile, since the two septa divide at the mid-ovary level. Consistently the four co-lateral ovules which are anatropous and bitegmic are supplied by four free placentals. The placentals supplying the two ovules of a given carpel have had a common origin in a single pedicel bundle. Raphides characterize post-fertilization ovaries in all species. ADrusa-type of embyro sac formation shown forM. dilatatum corresponds with that known for the other species. An internal stigmoidal tissue system involving micropylar obturators extends from the base of each locule through the hollow stylar canal. Temporal separation occurs between male and female meiosis (protandry), and outbreeding is further promoted by terminal septal glands functioning as nectaries and the synchronized closure of the common carpellary cavity by inter-digitating papillae on the inner septal margins. This work was supported in part by the U.S.-Japan Cooperative Science Program Grant GF-41367, the Japanese Soceity for the Promotion of Science and Grant-in-Aid No. 934053 from the Ministry of Education, Japan.     

HYBRIDIZATION AND FLORAL VASCULARIZATION

Hillson, Charles J. (Pennsylvania State U., University Park.) Hybridization and floral vascularization. Amer. Jour. Bot. 50(10): 971–978. Illus. 1963.—The floral steles of 6 synthetic hybrid mints, representing the F₁ generation of a cross between Mentha spicata strain 199 and Mentha aquatica, were compared with each other and with the steles of the parents. Comparisons of the level of trace divergence, ovary wall vascularization, presence or absence of a nectary, and the nature of the gaps associated with dorsal carpellary bundles show that floral vascularization is an inherited character. Although slight male dominance is indicated in the hybrid steles, anatomical features of both parents are evident. Thus, while vascular tissue may be conservative when phylogenetic reduction of floral parts takes place through adnation and/or connation, stelar modification through hybridization is documented.     

FLORAL ONTOGENY OF ILLICIUM FLORIDANUM,WITH EMPHASIS ON STAMEN AND CARPEL DEVELOPMENT

The ontogeny of the flower and fruit of Illicium floridanum Ellis, the Star Anise, was investigated. Each of 5 or 6 bracts in each mixed terminal bud subtends either a vegetative or floral bud. The solitary flowers occur in terminal or axillary positions. Each flower has 3–6 subtending bracteoles arranged in a clockwise helix. The flowers in our material have 24–28 tepals, 30–39 stamens, and usually 13 (rarely 19) uniovulate carpels. Tepals and stamens are initiated in a low-pitched helix; carpels later appear whorled, but arise successively at different levels on the apical flanks. The floral apex is high-convex in outline with a tunica-corpus configuration; it increases in height and width throughout initiation of the floral appendages. Tepals, stamens, and carpels are initiated by one to several periclinal divisions in the subsurface layers low on the apical flanks, augmented by cell divisions in the outer layers of the corpus. The carpel develops as a conduplicate structure with appressed, connivent margins. Procambium development of floral appendages is acropetal and continuous. Bracteoles, tepals, stamens and carpels are each supplied by 1 trace; the carpellary trace splits into a dorsal and an ascending ventral sympodium. The latter bifurcates to form 2 ventral bundles. The ovular bundle diverges from the ventral sympodium. Ovule initiation occurs in a median axillary position to the carpel, an unusual type of ovule initiation. The fruit vasculature is greatly amplified as the receptacle and follicles enlarge. After carpel initiation an apical residuum persists which is not vascularized; a plate meristem develops over its surface to produce a papillate structure.     

Floral vasculature in Alpinia hainanensis in relation to the nature of the labellum in gingers

Observations presented here on floral vasculature in Alpinia hainanensis indicate that the labellum incorporates elements of five androecial members rather than two or three, as suggested by previous authors for Zngiberaceae flowers. The pedicel contains an outer ring and a central region of vascular bundles. Three carpellary dorsal bundles (CDs) and three alternatively arranged parietal bundles (PBs) separate from the central region successively. The remaining bundles of the central region run upwards and become the placental bundles to supply ovules. The placental bundles terminate between the top of the locular region and the base of the prolongation. The three PBs divides into about five strands respectively. Of which the outer strand enters into the petal being its midrib and the remaining strands move into the stamen adaxially being the vasculature of the functional stamen and the labellum abaxially being the lateral strands of the labellum. The three CDs divide into about five traces, of which the outer strand becomes the midrib of each sepal and the inner strand runs into the style. The remaining traces re‐unite, re‐divide again in the course up and the two adaxial sets of carpellary dorsals finally enter into the labellum being the marginal traces of it while the abaxial single strand enters into the labellum being its midrib. The two antero‐lateral glands receive small traces without lignified tube elements from the vascular plexus, which fonn in prolongation from both PBs and CDs and a few small strands in the ovary wall. There are no subulate appendages differentiated in the flower of Alpinia hainanensis. Hereby, the median of the sepals, both the marginal portions and the median of labellum, and the style have the same origin in vasculature from the CDs and so do the stamen, the lateral portions of labellum and the median of the petals from PBs. The labellum is supposed to represent three members of the outer androecial whorl by its two marginal portions and the median and two members of the inner whorl by its two lateral parts except the median.     

PHYLLOTAXIS AND VASCULAR ORGANIZATION OF THE CARPELS IN MICHELIA FUSCATA

Tucker , Shirley C. (U. Minnesota, Minneapolis.) Phyllotaxis and vascular organization of the carpels in Michelia fuscata. Amer. Jour. Bot. 48(1): 60–71. Illus. 1961.—Phyllotaxis pattern and vascular organization are closely related in the floral receptacle of Michelia fuscata (Magnoliaceae). The carpels arise in a spiral or helix. They are initiated alternately along each of 7, 8 or 10 helical parastichies according to a complex repetitive sequence. The pattern of the dorsal carpellary trace fusions is orderly for each of the 10 flowers investigated. The dorsal carpellary traces in each parastichy diverge from the same vascular sympodium. Among flowers one finds differing numbers of parastichies, differing angles of divergence, and varying sequences of parastichies which reflect the order of carpel initiation. The angle of divergence, although consistent for any 1 parastichy in a flower, can vary greatly between parastichies. The nature and importance of the organizers which determine appendage position at the apical meristem are considered. Changes in apical size, configuration, and activity are shown to be related to phyllotaxis.     

FLORAL DEVELOPMENT AND VASCULATURE IN HYDROCLEIS NYMPHOIDES (BUTOMACEAE)

The flower of Hydrocleis nymphoides consists of three sepals which arise in spiral succession, three simultaneously arising petals, numerous stamens and staminodia which arise in centrifugal order, and six carpels. A residual apex remains at maturity. The first-formed members of the androecium are stamens and the later-formed members are staminodia which develop below the stamens and which become outwardly displaced during expansion of the receptacle. The androecium is supplied by branching vascular trunk bundles. The carpels are completely open but the ventral margins are slightly conduplicately appressed basally. A single dorsal bundle provides the stigmatic area with vascular tissue, and a network of small placental bundles supplies the numerous laminar ovules. There are no clearly defined ventral bundles. It is suggested that Hydrocleis nymphoides is neither the most primitive nor the most advanced member of the family. A pattern of phylogenetic reduction in the androecium and receptacle is suggested for the entire family.     

ORIGIN AND DEVELOPMENT OF THE TERMINAL CARPEL IN PSEUDOWINTERA TRAVERSII

Flowers of Pseudowintera traversii (Buchan.) Dandy possess a terminal unicarpellate gynoecium. The present study of carpel morphogenesis was initiated for the purposes of (1) providing additional developmental documentation of the occurrence of terminal carpels in the Winteraceae and (2) comparing the mode of initiation and development of the ascidiate terminal carpel of P. traversii with the essentially conduplicate terminal carpel of Drimys lanceolata. Following its axillary origin, the floral apex of P. traversii initiates 2–3 connate sepals, 5–6 petals, 4–15 stamens, and usually a single terminal carpel, in acropetal succession. Bicarpellate gynoecia may occur with a frequency of up to 15 % on a given plant. The floral apex is zonate and shows increased expression of its zonation during later stages of floral development. The terminal carpel is ascidiate from inception and originates as a cylindrical growth around the entire circumference of the floral apex; transformation of the floral meristem into a carpel primordium terminates apical growth of the floral axis. Carpel growth continues to be cylindrical and is mediated by a ring of marginal and submarginal initials at its summit. Earlier and more extensive division of initials and their derivatives on the dorsal rim causes the primordium to become canted adaxially, shifting the apical cleft to a subterminal adaxial position. Continued marginal meristematic activity results in closure of the cleft as well as elevation and elaboration of the stigmatic crests. Five to seven bitegmic ovules are initiated at the same time as crest elaboration and arise in two rows from the adaxial (laminar) position. Carpel maturation is signified by tannin deposition and oil cell differentiation, beginning at the base and proceeding acropetally; carpel margins bordering the cleft are the last to differentiate. Carpel procambialization is continuous and acropetal from inception, with the dorsal median bundle differentiating before the ventral strands. The significance of occasional bicarpellate flowers is discussed.     

Comparative morphology of the carpel in the Liliaceae: Baeometra, Burchardia and Walleria

The pistils in Baeometra, Burchardia and Walleria ate tricarpellate, and their ovules are mostly bitegmic. Baeometra has free styles and deep septal invaginations between the carpels. Its pistil is innervated by three dorsal bundles, three compound septal bundles (each of which may divide into two simple septal bundles above), six placental bundles, and six adjoining auxiliary placental bundles. The pistil of Burchardia resembles that of Baeometra , except that there are six simple septal bundles throughout and no auxiliary placental bundles. In Walleria the wings of adjoining carpels are completely fused (except for rare septal glands); there is a single compound style; additional vascular tissue is present in the central axis of the pistil up to the lowermost ovules; the carpels are fused with the floral cup above the base of the locules; and raphide idioblasts are present. Walleria has six "ventral" bundles, each of which appears to be the fusion product of a placental bundle with a simple septal bundle. Tribal affinities of these genera are discussed.     

MORPHOLOGICAL STUDIES OF THE NYMPHAEACEAE SENSU LATO. XVII. FLORAL ANATOMY OF ONDINEA PURPUREA SUBSPECIES PURPUREA (NYMPHAEACEAE)

Classification and phylogeny of the Nymphaeaceae are unresolved. This study provides floral anatomical data that will assist in elucidating generic interrelationships and systematic relationships to other taxa of angiosperms. The floral anatomy of Ondinea purpurea den Hartog subsp. purpurea has been examined utilizing light microscopy. The peduncle possesses stelar vascular bundle complexes and cortical vascular bundles. Cortical bundles terminate within the peduncle. Each bundle complex consists of 2 collateral bundles on the same radius, the inner bundle inverted; 2 protoxylary lacunae occur yet differ in structure and function. Progressing acropetally, the inner xylary lacunae become discrete mesarch strands surrounded centrifugally by a vascular cylinder formed by divisions and anastomosing of the bundle complexes. Together these become the massive receptacular vascular plexus. The plexus provides collateral traces to the floral organs. Each sepal receives 3 traces that separate from the plexus as 1–3 lateral traces. Petals are absent and no vestigial petal traces have been observed. Distally, the plexus forms several large strands of connate gynoecial and androecial traces termed the principal vascular bundles (PVBs). Ventral veins separate from the PVBs and the latter extend acropetally through the outer ovary wall. Branches of the ventrals and PVBs contribute to septal vascular reticula from which each ovule is supplied by one vascular bundle. Each stamen receives 1 trace from branches of the PVBs. The ventrals and PVBs terminate within the carpellary lobes. A comparative anatomical study is offered that supports the inclusion of Ondinea in the Nymphaeaceae sensu stricto.     

COMPARATIVE MORPHOLOGY OF THE CARPEL IN THE ROSACEAE. IV. POMOIDEAE: CHAMAEMELES,COTONEASTER, DICHOTOMANTHES,PYRACANTHA

The carpels of Chamaemeles, Cotoneaster, Dichotomanthes, and Pyracantha tend to be separate from one another, their sutures tend to be closed, and they become more or less bony at maturity. However, aside from having collaterally placed ovules, they do not appear to be structurally similar. There seem to be 2 different evolutionary trends in the ovular bundle–wing bundle relationship: in Pyracantha, progressive fusion between the ovular bundle and the wing bundle has led to the formation of a “ventral” bundle; in Cotoneaster, and possibly Chamaemeles, the wing bundle has become reduced and rather attenuated. A primitive pomoid state may be represented by the carpel of Dichotomanthes, which is completely free of the floral cup and in which wing and ovular bundles are separate. Differences in sutural closure appear only in Cotoneaster, and in species of that genus the wing bundles and ovular bundles tend to be fused if the suture is closed, and separate if it is open.