Embryology ofCrocus thomasii (Iridaceae)

The embryology ofCrocus thomasii is described. Male meiosis is of simultaneous type, and gives rise to starchy microspores which develop into lipoid pollen grains; these are two-celled and show a spinulate acolpate, abaculate exine lacking apertures. The tapetum is glandular and its cells become bi- or sometimes multinucleate. The ovule is anatropous and bitegmic; the inner integument forms the micropyle. Megasporogenesis is heteropolar with starch accumulation in the functional chalazal megaspore. Embryo sac development conforms to thePolygonum type. The endosperm development is nuclear. The embryo develops according to the Caryophyllad type. In the ripe seed it is differentiated and enveloped by a starchy cellular endosperm. The embryological characters observed strongly favour a close relation betweenC. thomasii andC. sativus.     

Embryology and systematic position ofLiparis (Orchidaceae)

The embryology ofLiparis paradoxa andL. rostrata has been studied. The young anther wall consists of an epidermis, endothecium, three middle layers and secretory tapetum with uninucleate cells. In the mature anther, two or three sub-epidermal layers develop fibrous thickenings. The anther wall development corresponds to the massive type. Simultaneous cytokinesis results in decussate, isobilateral, linear, T-shaped and tetrahedral pollen tetrads. The pollinia are compact and at anthesis the pollen grains are 2-celled. Ovules are anatropous, bitegmic and tenuinucellate. Both the integuments are dermal in origin and 2-layered. Development of female gametophyte is of the monosporic, 8-nucleate type. Double fertilization occurs. The primary endosperm nucleus degenerates. The mature embryo is organized from the derivatives of tiers 1, 1, m, and n. Its development conforms to a variation of the Onagrad type. The seed coat is formed entirely by the outer layer of the outer integument. There are three sterile and three fertile valves in the ovary. In the prefertilization stages valves consist of parenchymatous cells. After fertilization, the sterile valves become sclerenchymatous whereas the fertile valves remain parenchymatous. The embryological characters support the disputed systematic position ofLiparis within subtribeLiparidinae ofEpidendreae.     

Embryology ofMalaxis saprophyta,with comments on the systematic position ofMalaxis (Orchidaceae)

InMalaxis saprophyta, anther wall development corresponds to the Monocotyledonous type. The uninucleate tapetum is of secretory type and the endothecium develops U- and V-shaped thickenings on the inner tangential and radial walls. Cytokinesis is simultaneous; tetrahedral, isobilateral and T-shaped tetrads are formed which are compactly aggregated in pollinia. At anthesis the microspore tetrads are 2-celled. The ovule is anatropous, bitegmic and both integuments are dermal in origin. A single hypodermal cell develops directly into a megaspore mother cell. Embryo sac development is predominantly monosporic and less often bisporic. Irrespective of the type of development, the mature embryo sac is 6-nucleate. Although double fertilization occurs, the primary endosperm nucleus degenerates. Embryogeny is of the Onagrad type. The mature embryo lacks differentiation into cotyledon, plumule and radicle. The reticulate seed coat is formed entirely by the outer layer of outer integument. There are three sterile and three fertile valves in the ovary. Although initially parenchymatous, the entire three sterile valves in the ovary and the upper half of the three fertile valves become sclerified after fertilization. The embryological characters support the disputed systematic position ofMalaxis within subtribeMalaxidinae ofEpidendreae.     

Embryology and relationships ofGyrocarpus andHernandia (Hernandiaceae)

Two representative genera of Hernandiaceae,Gyrocarpus andHernandia, were investigated embryologically to contribute to a better understanding of their respective evolutionary position. Comparisons with other lauralean families using Chloranthaceae or Annonaceae (as a representative of Magnoliales) as an outgroup of Laurales (if present, plus other related taxa) support a lauraceous affinity for the two genera because of the presence of ramified raphal vascular bundles at the chalaza (a synapomorphy), but do not provide evidence for the separation of Hernandiaceae from Lauraceae.Hernandia rather shares with Lauraceae two apomorphies (i.e., the seed pachychalazy and the ruminate seed) which may be homoplasies judged from results of cladistic and molecular studies published elsewhere.Hernandia is greatly divergent from an ancestral line common withGyrocarpus and is even diversified within the genus. Based on evidence from embryology as well as from other sources, it seems best to accept two separate subfamilies in Hernandiaceae as usually have been accepted: one is a derived subfamily Hernandioideae, and the other a less specialized Gyrocarpoideae.     

Embryology of Gomortegaceae (Laurales): characteristics and character evolution

The embryological characteristics of Gomortegaceae, which are poorly understood, were investigated on the basis of Gomortega nitida, the only species of the family, to understand better the evolution of this group within Laurales. Comparisons with other Laurales and Magnoliales (a sister group of Laurales) show that Gomortega has many embryological features in common with the other lauralean families. Notably, Gomortega shares a testa without or with at best only a poorly developed mesotesta as a synapomorphy with all other Laurales. The genus further shares anthers dehisced by valves as a synapomorphy with the other Laurales (except for Calycanthaceae and Monimiaceae), and a non-multiplicative testa and bisporangiate anther as synapomorphies with Atherospermataceae and Siparunaceae (although the non-multiplicative testa occurs as a homoplasy in Monimiaceae, and the bisporangiate anther in Monimiaceae pro parte, Lauraceae pro parte and Hernandiaceae, respectively). Gomortega shows simultaneous cytokinesis to form pollen grains, a one-celled ovule archesporium and non-specialized chalaza, all or part of which may be synapomorphies shared with Atherospermataceae. Gomortega appears to have no embryological autapomorphies, but further comparison with Atherospermataceae is required.Kweon Heo and Yukitoshi Kimoto contributed equally to this work.     

Embryology of Siparunaceae (Laurales): characteristics and character evolution

Embryological characters of Siparunaceae, which are poorly understood, were studied on the basis of two constituent genera, an African Glossocalyx and a South American Siparuna, to better understand their evolution within Laurales. These two genera have many embryological characteristics in common with the other lauralean families. Noticeably, they share the multi-celled ovule archesporium (uncertain in Glossocalyx) as a synapomorphy with all the other lauralean families except Lauraceae, the anthers dehisced by valves as a synspomorphy with all the other lauralean families except Calycanthaceae and Monimiaceae, and the bisporangiate anther as a synapomorphy with Gomortegaceae and Atherospermataceae. Siparunaceae are, however, distinct from all other laularean families in having unitegmic ovules that were derived from bitegmic ovules, probably due to an elimination of the outer integument. Likewise, the lack of the testa (i.e., developed outer integument), the "endotegmic" seed coat, and the perichalazal seed at maturity are also characteristics of Siparunaceae. Within the family, Siparuna differs from Glossocalyx in having plural tetrads of megaspores and plural, starchy-rich, one-nucleate, tubular embryo sacs (autapomorphies). On the other hand, Glossocalyx is characterized by having bilaterally flattened seeds (autapomorphy). Although functional aspects of those autapomorphies are uncertain, both Glossocalyx and Siparuna show evolution in different embryological characters.     

Embryology and relationships ofSuriana maritima L. (Surianaceae)

An intensive study of the embryology ofSuriana maritima L. is made to provide the information for discussing relationships and systematic position of the genus which is uncertain yet. Notable embryological features ofSuriana include: ovular archesporium multi-celled; ovule unitegmic, campylotropous, and crassinucellate with a nucellar cap; obturator not formed; ovule and seed pachychalazal; chalazal haustorium of endosperm formed; mature seed exalbuminous. Comparisons with possibly related families suggest thatSuriana is distinct from any of the families discussed but best resembles Rutaceae (and Simaroubaceae). Until a study onStylobasium and several other genera, which might be closer toSuriana, comes up in future, we tentatively support the placement ofSuriana as a monotypic family Surianaceae in Rutalessens. Takhtajan.     

Embryology ofKyllinga monocephala (Cyperaceae) and its systematic position

Aspects of the life history ofKyllinga monocephala are described. Anther wall development corresponds to the Monocot type. The endothecium shows spiral thickenings. The tapetum is glandular and has uninucleate cells. Ubisch granules are present. Mature pollen grains (pseudomonads) are 3-celled at maturity. Ovules are bitegmic, crassinucellate and develop a funicular obturator. The embryo development conforms to theJuncus-variation of the Onagrad type. Endosperm, seed coat and pericarp are described.     

Studies on systematic embryology inScilla (Hyacinthaceae)

Scilla persica and 5 species of the so-calledS. hohenackeri group, namely,S. furseorum, S. puschkinioides, S. vvedenskyi, S. hohenackeri, andS. greilhuberi, have been investigated embryologically with special reference to embryo sac and endosperm development.Polygonum-type embryo sac development was stated inS. puschkinioides andS. greilhuberi. 8-nucleate, normally structured embryo sacs, which could not be specified further due to sparse availability of the material, were stated inS. furseorum, S. vvedenskyi, andS. hohenackeri. InS. persica the embryo sac develops according to the bisporicAllium-type. In most species endosperm development was stated to be nuclear, exceptS. hohenackeri, where the type could not be specified. Other traits of possible taxonomic significance are the number of layers in the outer integument, which is mostly 4, or 5–6 inS. furseorum, and the occurrence of polyploid versus haploid and early degenerating antipodal nuclei, the latter occurring only inS. persica andS. furseorum. These embryological characters may be useful for assessing taxonomic relationship of the present species with other allied groups withinScilla, in particular, theS. siberica alliance,S. messeniaca, and theS. bifolia alliance. TheAllium-type embryo sac, which occurs inS. persica, is also characteristic for theS. siberica alliance, and may be a common derived character. Lack of antipodal polyploidization, as characteristic forS. persica andS. furseorum, occurs also in theS. siberica alliance, and is perhaps another common derived trait indicating phylogenetic relationship. Nuclear endosperm development is more frequent in spring-flowering squills than helobial development, which has previously been stated inS. messeniaca, some species of theS. siberica alliance, and inS. litardierei. While helobial endosperm may be primitive forHyacinthaceae in general, it may, by reversal, also occur as a derived character, at least in some species of theS. siberica alliance.     

The embryology and relationships ofPenaeaceae (Myrtales)

Two species ofPenaeaceae (Penaea mucronata andSaltera sarcocolla), a unique South African family ofMyrtales, were investigated embryologically.Penaeaceae clearly agrees with otherMyrtales in its basic embryological characteristics, and further is characterized by its highly specialized features: ephemeral endothecium, 16-nucleatePenaea-type embryo sac, and unique ovular form. A wider range of affinities of families includingPenaeaceae, Oliniaceae, Rhynchocalycaceae, Alzateaceae, andCrypteroniaceae sensu stricto, as well as a possible common divergence from an ancestral line leading toLythraceae and/orMelastomataceae, are discussed on embryological and other grounds.     

Embryology of Laurales: a Review and Perspectives

s. str. and Siparunaceae) are probably defined by a multi-celled ovule archesporium and a crushed mesotesta. Within Laurales, 16 embryological characters are found to be diversified, including the number of microsporangia (four or two), mode of anther dehiscence (by slits or valves), the number of archesporial cells in an ovule (one, two or more), and so on. Their respective evolutions were traced on a phylogenetic tree generated from molecular and morphological data, supporting that Calycanthaceae represent the earliest branch and are sister to a clade comprising six remaining families with a valvate anther dehiscence as already suggested. However, because of a lack of sufficient data from each family of Laurales, embryological characters often have alternative possibilities with respect to where they have evolved. More extensive and/or intensive studies of individual families are needed to clarify their exact evolutionary relationships. Received 19 March 2001/ Accepted in revised form 6 June 2001     

Embryology ofCordia sebestena (Boraginaceae)

Sporogeneses and gametogeneses inCordia sebestena are described. Anther wall develops according to the Dicotyledonous type. Pollen grains are three-celled at the time of dehiscence. The occurrence of enlarged, precociously developing, densely cytoplasmic cells toward the proximal end of the anther and between adjacent pollen sacs is a unique feature in this species. The possible functions of these cells are discussed. A placental obturator develops simultaneously with the ovules. The dual origin of parietal tissue (from nucellar epidermis and the archesporial initial) is an unusual feature in this species. Megagametophyte development is monosporic or (occasionally) bisporic. Megaspore tetrads are linear or T-shaped. Double dyads and tetrads are frequently observed.—Maintainance of subfamily status forCordioideae is supported.     

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.     

Studies in the embryology of the diandrous orchidCypripedium cordigerum (Cypripedieae,Orchidaceae)

The anther wall layers ofCypripedium cordigerum are six to eight. The glandular tapetum is 2- or 3-layered and its cells are uninucleate. Simultaneous cytokinesis results in decussate, isobilateral and tetrahedral pollen tetrads. Ripe pollen grains are 2-celled. The mature ovules are anatropous, bitegmic and tenuinucellate. Both the integuments are dermal in origin and 2-layered. The inner integument alone forms the micropyle. The female gametophyte is 6-nucleate and bisporic. The reduction of nuclei is due to the strike phenomenon. Double fertilization occurs. The primary endosperm nucleus divides to form two free endosperm nuclei. The mature embryo is undifferentiated. The cells ca, m and n contribute to the embryo. The suspensor is single-celled. The seed coat is formed entirely by the outer layer of the outer integument. There are three sterile and three fertile valves in the ovary. In the prefertilization stages these valves consist of parenchymatous cells with starch and raphides. After fertilization, the sterile valves develop sclerotic cells whereas the fertile valves remain parenchymatous. The pericarp structure and embryological features support the retention of tribeCypripedieae within theOrchidaceae.     

川东獐牙菜(龙胆科)的胚胎学研究

利用石蜡切片技术,对川东獐牙菜(Swertia davidii)的胚胎发育过程进行显微观察,并根据现有资料,对獐牙菜属的几种植物进行了比较胚胎学研究。结果表明:川东獐牙菜花药四室,药壁发育为基本型,绒毡层异型起源,为腺质绒毡层,发育后期药室内观察到的绒毡层核是早期该层细胞有丝分裂凸入药室并原位退化形成的,中层细胞3层,药室内壁退化,花药壁表皮宿存,细胞柱状伸长,纤维状加厚;小孢母细胞减数分裂为同时型,四分体排列方式主要为四面体形和左右对称型,少数为"T"形和十字交叉形,成熟花粉为2-细胞类型;子房2心皮、1室,侧膜胎座;薄珠心,单珠被,倒弯生胚珠,大孢子母细胞减数分裂形成4个大孢子直线形排列,合点端的大孢子具功能,雄配子体发育为蓼型;2个极核在受精前融合为1次生核,合点端3个反足细胞宿存,每个细胞均多核和异常膨大,形成明显的反足吸器,并在胚乳之外形成染色较深的类似"外胚乳"结构;珠孔受精,受精作用属于有丝分裂前类型;胚乳发育为核型,胚胎发育为茄型;果实成熟时,种子发育至心形胚阶段;反足细胞在龙胆科一些短命植物中的宿存与分裂具有重要的生殖适应与进化意义。     

The systematic significance of surface features of theBalanophora tuber (Balanophoraceae)

The surface ofBalanophora tubers consists of a nonepidermal layer made up of two distinctive types of cells, armature cells and stellate wart cells. Both cell types are provided with a heavy wall, and are dead at maturity. Stellate warts in the three species investigated,B. elongata, B. fungosa, andB. hansenii, séem to be uniform in appearance, but armature cells are extremely distinctive for each species. They are present in large, agglomerate masses in the first, singly or in very small clusters in the second, and as completely free, individual, acicular cells in the third species. Such differences are believed to be significant systematically, and the separation ofB. hansenii is thus probably justified. Notwithstanding superficial similarities, stellate warts do not seem to be comparable to the lenticels of other plants.