Unilocular Ovary Research Articles

Embryology and seed development ofDactyliandra welwitschii Hook. f.

The embryology and seed development ofDactyliandra welwitschii Hook. f., a monotypic species of Cucurbitaceae, is studied. The inferior, tricarpellary, unilocular ovary with parietal placentation bears anatropous, bitegmic and crassinucellate ovules singly at the tip of each lobe of the bifid placenta. The deep seated megaspore mother cell undergoes meiosis to form a linear tetrad of megaspores. The chalazal megaspore is functional and embryo sac development follows the Polygonum type. Fertilization is porogamous and pollen tube is persistent.

The Affinities of Lithophytum: A Transfer from Solanaceae to Verbenaceae

Lithophytum violaceum Brandegee, until recently known only from a single Mexican collection, has been considered anomalous since it was first described in 1911. This genus was originally assigned to the Solanaceae, but our reexamination of it shows that this relationship is highly unlikely. A plant of xeric habit with small emarginate leaves, it is different from any other known genus. The flowers have five sepals, and the sympetalous corolla is campanulate or salverform. The five equal epipetalous stamens surround a unilocular ovary with two parietal anatropous ovules. Style and stigma are absent, and the locule of the ovary is exposed to the outside by an apical pore. The wood, young stem, leaf, floral anatomy, and pollen were studied in detail, and the aggregate of morphological features accords well with the Verbenaceae.

Development and structure of seed inTacsonia Juss. andPassiflora L.

Tricarpellary, syncarpous, unilocular ovary bears horizontal, bitegmic, crassinucellate and antropous ovules on three parietal placentae. Micropyle iszig-zag formed by both the integuments. The embryo sac is of Polygonum type and the pollen tube is persistent. The development of endosperm is nuclear and at maturity it becomes ruminate. The mature embryo is spatulate with two thin cotyledons and a short stubby hypocotyledonary region.

Embryological studies in Gentianaceae

Embryology ofEnicostema hyssopifolium (Willd.) Verdoorn. andExacum saulieri L. has been investigated. Anther wall development is of the dicotyledonous type and at maturity consists of the epidermis, fibrous endothecium, 1–2 middle layers and the tapetum which is uniseriate with uninucleate cells. Connective tapetum is also differentiated. Pollen grains are triporate and 3-celled at anthesis. Pollen degeneration at various stages of development is common. The bicarpellary, syncarpous and unilocular ovary bears anatropous, unitegmic and tenuinucellate ovules on parietal placentae. Embryo sac development is of the polygonum type. Fertilisation is porogamous and the endosperm isab initio nuclear. Embryogeny is of the Solanad type.

Contributions to the Flora of Tropical America: LXIX. A New Genus of Peridiscaceae

Peridiscus lucidus Benth. was first found by Spruce on the Rios Uaupes and Pacimoni and was recently collected near Manaus ( on the Rio Tarumi) by the late Dr. A. Ducke. Originally described by Bentham (1862) in the 'Genera Plantarum', it was figured with a fresh description by D. Oliver (1896) in Hooker's 'Icones Plantarum'. These authors both placed it, with some doubt, in the Bixaceae and it was maintained in that family by Eichler (1871) in Martius's 'Flora Brasiliensis', and at the end of the Flacourtiaceae, with doubt, by Dr. O. Warburg (1893) and E. Gilg (1925) in the first and second editions of the 'Pflanzenfamilien'. Recently, however, the plant has been studied afresh from Ducke's much better material, by Dr. J. G. Kuhlmann (I950). This author, who was apparently ignorant of Oliver's figure and description, after pointing out errors in the descriptions of Bentham, Eichler, Warburg and Gilg, rejected Peridiscus, not only from the Flacourtiaceae, but also from the Olacaceae and, finally, the Capparidaceae, in which latter family it had been placed by H. Hallier (I908). He proceeded to treat it as constituting a new family Peridiscaceae, the salient characters being the presence of stipules, apetaly, imbricate sepals, numerous stamens with monothecous anthers, a conspicuous disk surrounding the unilocular ovary, pendulous ovules from its apex, 3-4 free styles, a large, solitary seed with abundant horny endosperm, and a minute, straight embryo placed laterally in a shallow cavity near its apex. The characters of the endosperm and the embryo, he noted, are found in the Santalales. The family Peridiscaceae is accepted by Dr. J. Hutchinson (I959) in the new edition of his 'Families of Flowering Plants', and is placed in the Tiliales, 'for want of a better place', but he seems not to have read Kuhlmann's emended description and comments, for he repeats the errors of his predecessors, describing the sepals as valvate, the anthers (also figured) as 2-locular and the seed as without endosperm. Some of these characters could have been verified by examination of Ducke's specimens of Peridiscus lucidus at Kew. Again, it must be stated that the Peridiscaceae appears in Hutchinson's great 'Key to the Families' in a section with exstipulate leaves on p. 91, under Group 12, although he rightly mentions the stipules in his description of the family. The Potaro Valley material lacks fruits and seeds, but shows nearly all

The Genus Schismatoglottis (Section Philonotion) in America

The genus Philonotion Schott is included in Schismatoglottis, forming the American section of an otherwise Asian group. Two species are recognized in this section: 1) S. americana, known only from Surinam, and 2) S. spruceanum, here transferred from the genus Philonotion and represented by two varieties: var. spruceanum of Amazonian Venezuela and adjacent Colombia, and var. williamsii of Amazonian Venezuela only. GEORGE S. BUNTING, Missouri Botanical Garden, 2315 Tower Grove Ave., St. Louis 10, Missouri. The genus Philonotion was published by Schott (Gen. Aroid. 54. 1858.) to accommodate a single Spruce collection from Amazonian Brazil. For a century, this monotypic genus has been maintained and included in various works on the Araceae. Known from the type collection only, its alliance was variously interpreted. Schott (Prod. Syst. Aroid. 317. 1860.) judiciously placed Philonotion in the subtribe Adeloneminae immediately preceding subtribe Schismatoglottidinae. Engler (Pflanzenreich IV. 23(55): 24. 1912.) included it in the subtribe Philodendrinae following Philodendron. This latter treatment is curious, since that author noted the parietal placentation, the distinctive stamens with apical pores, and the nonscandent habit of growth of Philonotion. In contrast, placentation in Philodendron is axile, the stamens are of an entirely different nature, and the species are predominantly scandent. The deciduous nature of the blade of the spathe and staminate portion of the inflorescence after anthesis in Philonotion further differentiate these two genera. Philonotion falls clearly into the subtribe Schismatoglottidinae as defined by Engler (l.c. p. 24). Indeed it appears that Philonotion is the American section of the otherwise Malaysian genus Schismatoglottis.1 The first and only American species to be described in the latter genus is S. americana Jonk. & Jonk. Following its description (Acta Bot. Neer. 2(3):362. 1953.), the authors commented upon the apparent relationship between Philonotion and Schismatoglottis. The current study has verified the close affinity of these two genera, and has demonstrated clearly that S. americana is congeneric with material referred by other workers to Philonotion. Philonotion was initially characterized by a unilocular ovary bearing one parietal ovule. Recent collections that are undoubtedly conspecific with the type of this genus (P. spruceanum Schott) have either one or two parietal placentae each bearing one or two ovules, and the unilocular ovary may thus contain one to four ovules. The Malaysian Schismatoglottii commonly have ten or more ovules per ovary attached along three parietal placentae. With the exception of the fewer ovules, however, there is no constant floral character separating Philonotion from Schismatoglottis. Generally, an occasional staminode is found among the pistillate Issued March 31, 1960. 1Similar disjunction exists in other aroid genera. Homalomena is a predominantly Asian genus of about eighty species, six or seven of which occur only in America and have characters diverse enough to be considered as a separate section of the genus by Engler. A similar disjunction occurs in the genus Arisaema. One species of the otherwise American genus Spathiphyllum is native in Indonesia and the Philippines. (69) This content downloaded from 157.55.39.104 on Mon, 20 Jun 2016 05:34:41 UTC All use subject to http://about.jstor.org/terms [VOL. 47 70 ANNALS OF THE MISSOURI BOTANICAL GARDEN flowers in the latter genus, and some species have a sterile appendage of the spadix. The American species, previously referred to Philonotion, exhibit neither of these characteristics, but rather possess one outstanding vegetative feature apparently not found in any Asian species-the aristate or subcaudate apex of the leaf blade. Despite these differences, it seems prudent to reduce Philonotion to the rank of section under Schisrnataglottis.2 SCHISMATOGLOTTIS section Philonotion (Schott) Bunt. stat. nov. Philonotion Schott, Gen. Aroid. t. 54. 1858.

On the probable origin of the unilocular ovary of the Compositæ from the Stylidiaceæ

It is suggested that the unilocular ovary of the Compositae may have originated as a result of the gradual suppression or incomplete development of the septum separating the two locules in the ovary of the Stylidiaceae. It is also possible that the unilocular condition of the Compositae may have been derived as a result of abortion of one of the locules, for, this tendency is already evident in certain species ofStylidium likeS. adnatum.