We present phylogenetic analyses of Malpighiales, which are poorly understood with respect to relationships within the order, using sequences from rbcL, atpB, matK and 18SrDNA from 103 genera in 23 families. From several independent and variously combined analyses, a four-gene analysis using all sequence data provided the best resolution, resulting in the single most parsimonious tree. In the Malpighiales [bootstrap support (BS) 100%], more than eight major clades comprising a family or group of families successively diverged, but no clade containing more than six families received over 50% BS. Instead, ten terminal clades that supported close relationships between and among families (>50% BS) were obtained, between, for example, Balanopaceae and Chrysobalanaceae; Lacistemataceae and Salicaceae; and Phyllanthaceae and Picrodendraceae. The monophyly of Euphorbiaceae sens. str. were strongly supported (BS 100%), but its sister group was unclear. Euphorbiaceae sens. str. comprised two basally diverging clades (BS 100%): one leading to the Clutia group (Chaetocarpus, Clutia, Pera and Trigonopleura), and the other leading to the rest of the family. The latter shared a palisadal, instead of a tracheoidal exotegmen as a morphological synapomorphy. While both Acalyphoideae (excluding Dicoelia and the Clutia group) and Euphorbioideae are monophyletic, Crotonoideae were paraphyletic, requiring more comprehensive analyses.

Among the Cycadales (Cycadaceae and Zamiaceae), the Zamiaceae are known to be insect-pollinated. In contrast, the Cycadaceae are still considered wind-pollinated, although some doubt has been cast on several species, including Cycas revoluta. Using a large population of C. revoluta on Yonaguni Island (Okinawa, Japan), we performed exclusion experiments, documented insects from male and female cones, and analyzed the morphology of the apical part of the ovule to determine the pollination method of this species. Insect exclusion resulted in a notable reduction in seed set, except in a few individuals growing near male cones. The amount of airborne pollen was abundant within a 2-m radius of male cones but decreased markedly beyond this distance. Pollen grains of C. revoluta were found on the body of Carpophilus chalybeus (Nitidulidae, Coleoptera), one of a few species of insects collected from both male cones and female cones far from males. We conclude that C. revoluta relies on both wind (anemophily) and insect pollination (entomophily), although such anemophily is restricted to female trees growing within a 2-m radius of male trees. The nitidulids are not host specific to this cycad and primarily feed on plant tissue but serve as pollinators during pollen release. Cycas revoluta appears to be in an initial mode of animal pollination, as opposed to the host-specific insect pollination observed in most Zamiaceae.

A combination of embryological characteristics clearly defines Myrtales as comprising Combretaceae, Lythraceae (including Punicaceae and Sonneratiaceae), Melastomataceae, Myrtaceae, Onagra-"core" ceae, Oliniaceae, Penaeaceae, and Trapaceae, a circumscription that agrees with that of the Myrtales given by Dahlgren and Thome (1983). The ordinal characteristics are: 1) anther tapetum glandular, 2) ovule crassinucellate, 3) inner integument 2-layered (except in Syzygium), 4) micropyle formed by both integuments (except in Syzygium and Trapa\ 5) antipodal cells ephemeral or absent, 6) endosperm formation Nuclear type and 7) seed exalbuminous. Haloragaceae, Lecythidaceae, and Thymelaeaceae definitely should be excluded from Myrtales on the basis of differences in three or more of these primary defining characteristics. On the other hand, embryological evidence does not contradict the possibility of a relatively close relationship between Elatinaceae and Myrtales, even though an overall consideration of their features seems to make such a relationship seem less hkely. Embryological evidence indicates a considerable degree of heterogeneity in Rhizophoraceae, a family or group of families that is clearly not assignable to Myrtales.

We present the first study on the embryology of Amborela frichopoda Baill. which, based on recent analyses of multiple genes, was identified as the first branch in the angiosperm evolution. Comparisons with two other basal angiosperms (Nymphaeaceae and Illiciales), as well as with the other angiosperms, showed that most of the embryological features of Ambom//a are plesiomorphies. They include: the tetrasporangiate anther; the fibrous endothecium; the glandular tapetum composed of two-nucleate cells; two-celled mature pollen; formation of the hypostase; bitegmic and crassinucellate ovules; the Polygonum type embryo sac; ephemeral antipodal cells, a lack of vascular bundles in the integuments; ab infio Cellular type endosperm; non-pachychalzal ovule or seed; albuminous mature seed. Contrary to all previous descriptions, Amborela has hemianatropous, rather than anatropous or orthotropous, ovules. For the determination of the polarity of ovule curvature as well as of some other characters such as the presence or absence of the nucellar cap and the obturator, the formation of the micropyle, and seed coat structure, additional studies on Nymphaeaceae and llliciales are needed.

In contrast to most angiosperms, in which fertilization occurs 1 or 2 days after pollination, in some plant orders, including the Fagales, fertilization is delayed from 4 days to more than 1 year, raising questions regarding why fertilization is delayed and where and how pollen tubes remain in the pistil during the delay. To answer these questions, we investigated pollen-tube growth in pistils of Fagus japonica (Fagaceae), which are tricarpellate and have six ovules, using light, fluorescence, and scanning electron microscopy. The ovules were immature at the time of pollination and required 5 weeks to become fully developed. During this 5 weeks, pollen tubes grew from the stigma to the embryo sac in association with the development of ovules and intermittently in three steps with two growth-cessation sites, i.e., on the funicle and near the micropyle. The number of pollen tubes was gradually reduced from many to one at the two growth-cessation sites, and fertilization occurred in one ovule that apparently developed earlier than the others in the pistil. Thus, delayed fertilization plays an important role in gametophyte competition and selection leading to nonrandom fertilization. Intermittent pollen-tube growth is also likely widespread in angiosperms because it is known in other Fagales and an unrelated order Garryales.

Ovule and seed structure in Euphorbioideae, one of the five euphorbiaceous subfamilies, is surveyed to evaluate its systematic implications on the basis of 79 species representing four of five tribes. All Euphorbioideae, like two other "uniovulate" subfamilies Acalyphoideae and Crotonoideae, but unlike most of two "biovulate" subfamilies Oldfieldioideae and Phyllanthoideae, consistently have a persistent and palisadal exotegmen composed of radially elongate, sclerotic, and pitted cells. Within Euphorbioideae, the tribe Stomatocalyceae (also with the palisadal exotegmen) is unusual in having vascular bundles in outer integument and clearly distinct from the remaining Euphorbioideae and the other "uniovulate" subfamilies. With the exclusion of Stomatocalyceae, Euphorbioideae are not anatomically divided into major groups such as a pseudanthial and a non-pseudanthial clade, but instead have some remarkable diversity within a tribe, a subtribe, and even a genus in the three ovule and seed characters: (1) the thickness of the inner integument, (2) the thickness of the outer integument, and (3) the presence or absence of an aril. Groups of genera and species wrapped by different combinations of their characteristics, however, are not necessarily harmonized with tribal or subtribal classifications available. Anatomical similarities and dissimilarities presented in this paper, as well as relationships among taxa presented in the classifications available, will be critically evaluated in the light of results of ongoing molecular phylogenetic analyses.

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