The flowering plant family Alseuosmiaceae comprises three genera of shrubs: Alseuosmia A. Cunn. from New Zealand; Memecylanthus Gilg and Schltr. and Periomphale Baill. (=Pachydiscus Gilg and Schltr.) from New Caledonia. These genera are readily excluded from their traditional position in the Caprifoliaceae by virtue of their alternate leaves, valvate corolla lobes and their southern hemisphere distribution. Four species of Alseuosmia, including one hitherto undescribed species, are accepted here. The New Caledonian genera are poorly represented in herbaria; they may each be monotypic. Condensed tannin (leucocyanidin) and ellagitannin are abundant in all Alseuosmia tissues. Other simple phenolic compounds here (as detected in acid hydrolysates) include quercetin, kaempferol, caffeic acid and p-coumaric acid. Triterpenoid saponins are abundant in leaf tissue; alkaloids and probably iridoid compounds too, are absent. Tannin is found throughout the ovary tissue of Alseuosmia and in the inner and outer epidermises of the ovular integument. The floral vascular anatomy is detailed for the Alseuosmiaceae and reviewed for eight allied families. No features of the vascular system imply particular affinity of the Alseuosmiaceae with any of these allies. Within this family the association of different morphological and anatomical floral features supports the contention that primitive characters tend to be associated with one another in their distribution throughout the members of a taxon. The primary vascular pattern in the stem of Alseuosmia is of an open (sympodial) nature. The mature nodal anatomy is 3-trace trilacunar. All genera have a stem endodermis with prominent Casparian banding, and in Alseuosmia at least this endodermis passes through the secondary and quaternary stages (lignification-suberisation of walls; accumulation of phenolic compounds) as found in a typical root endodermis. All species of Alseuosmia lack rays in the secondary wood, whereas memecylanthus and Periomphale have extremely tall (indefinitely-prolonged?) rays. The vessels of these genera are relatively primitive (end-plate angle c.10-19°, no bars per scalariform plate c.16-37), and thus are comparable to vessels of the Escalloniaceae and Caprifoliaceae. The root periderm has a cortical origin in Alseuosmia and the root pith is persistent. Multicellular uniseriate hairs are found in the leaf axils in all Alseuosmiaceae. Hairs with similar structure and development are found in some genera of Pittosporaceae but not, so far as is known, in other related groups. Within Pittosporum, these uniseriate hairs appear to be homologous with the T-hairs many species have. The chromosome number of 2n=18 probably characterises all the species of Alseuosmia. A. macrophylla A. Cunn. is an obligate outbreeder with an incompatibility mechanism operating at the stylar level, while A. pusilla is self-compatible. Pollinating agents for the species are unknown. No internal barriers to hybridism exist between A. macrophylla and A. banksii A. Cunn. and the hybrid swarm between these species is recognised here as A. X quercifolia A. Cunn. Neither do internal barriers exist between A. macrophylla and A. pusilla, but differences in flowering time and mode of breeding help to keep these species separate in the field. Mature pollen of Alseuosmia is trinucleate: the ovule is uni-tegmic-tenuinucellate. The distinctness of the Alseuosmiaceae is upheld and its affinities are suggested to be with the Escalloniaceae, and to a lesser extent, with the Pittosporaceae.
| Identifer | oai:union.ndltd.org:ADTP/276979 |
| Date | January 1976 |
| Creators | Gardner, R. O. (Rhys Owen), 1949- |
| Publisher | ResearchSpace@Auckland |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated., http://researchspace.auckland.ac.nz/docs/uoa-docs/rights.htm, Copyright: The author |
Page generated in 0.0014 seconds