Inaug.-diss.--Heidelberg, 1894. / Spine title: Anatomy of orchids. "Sonderabdruck aus 'Flora oder allgem. bot. Zeitung' 1894, Heft." Vita. Includes bibliographical references.

Relationship and interfertility of Habenaria dilatata (lursh) Hook.,H. hyperborea (L.) R.Br, and H. saccata Greene was studied. Intraspecific and interspecific crosses were made. Chromosome counts of the three species showed 21 pairs of chromosomes in the cells, except for a small green-flowered population from Manning Park with n = 42 which was considered tetraploid and possibly of hybrid origin. These counts agree with earlier ones for the three species. Since creation of the genus Habenaria Willd» these species have been included under tribe Ophrydeae, which now has been changed to Orchideae, subtribe Orchidinae to conform with the rulings of the International Code of Botanical Nomenclature (1959)* In spite of apparently close relationships the species maintain their distinctness, even when growing sym-patrically, indicating barriers to outcrossing, or for plants growing in northerly regions, a lack of pollinators. Autogamous tendencies have therefore developed and H. dilatata and H. hyperborea are outcrossing or autogamous when the need arises. H. saccata seems to be self-sterile. Microsporogenesis in the species studied follows that of other orchids. The archesporial cell directly becomes the spore mother cell. All descendants of this cell stay together and divide together, forming a massula or pollen packet. Pollen mitosis results in the 2-nucleate pollen grain which is shed as such. The generative nucleus divides in the pollen tube, producing the 2 sperm nuclei, as the tube enters the ovary. Only the chalazal megaspore is functional. Three simultaneous divisions produce the monosporic, 8-nucleate Polygonum-type embryo sac. Fusion of the polar nuclei is the rule and takes place before fertilization. Triple fusion follows, hut the primary endosperm nucleus begins to degenerate usually before the r-ypote starts to divide. An haustorial susy ensor develops, which does not take part in the construction of the embryo proper. The mature embryo is an un differentiated body of 50-60 cells, suspended in the air-filled cavity of the reticulate testa. It takes from 3-4 weeks from pollination to saturation of the embryo. Intraspecific crosses were all successful. Interspecific crosses produced a higher percentage of seed with well developed embryos in IT. hyperborea x H. saccata crosses than in crosses between H. riil tata and either of the 2 other species. The tetraploid plants were successful both as seed and pollen parents. Regular meiosis would indicate allopolyploid origin. Artificial pollinations showed that gene flow is possible and that artificial crosses are easy to make. In nature isolating mec'r an isms must rrevent the species from losing their identity although hybridization may take place under favourable conditions. Control plants of H. dilatata and H, hyperhorea not emasculated and not protected showed a full seed set, indicating autocamy, whereas unpollinated H. sancata yielded only empty seed. / Science, Faculty of / Botany, Department of / Graduate

The effect of adding pure cultures of Azotobacteraceae ad triacontanol to orchid protocorms and seedlings was studies to determine if significant enhancement of various growth parameters would result in axenic cultures of orchids.

published_or_final_version / Botany / Master / Master of Philosophy

published_or_final_version / Zoology / Master / Master of Philosophy

Orchid habitat has been destroyed for centuries and as a result many species, some not even discovered yet, have been lost. From the orchid hunters of the 17th and 18th centuries to the deforestation and reckless collection of orchid species today, orchids and their habitats have continued to be at risk. Efforts such as in situ conservation, an approach to protecting orchids in their natural habitat, and ex situ conservation, the protection and propagation of orchids outside their natural habitat in places such as seed banks, laboratories, herbariums, and botanic gardens, have helped to preserve orchid species all over the world. This work includes the design of a botanic garden centred on orchids and their conservation. Situated in Ecuador, the garden design incorporates research, education, and conservation in a way that is inspiring and delightful to the visiting public. Orchids are featured in the design of the garden, and the conservation of this plant family is emphasized. A history of botanic gardens explores the evolution of this specific type of garden, providing a background for modern-day design. Case study analyses of contemporary botanic gardens provides additional information and insight into the changing role of botanic gardens in the 21st century. This Practicum explores the creation of an educational garden that is also entertaining and challenges the notion of what a botanic garden is today and what it can be in the future.

Orchid habitat has been destroyed for centuries and as a result many species, some not even discovered yet, have been lost. From the orchid hunters of the 17th and 18th centuries to the deforestation and reckless collection of orchid species today, orchids and their habitats have continued to be at risk. Efforts such as in situ conservation, an approach to protecting orchids in their natural habitat, and ex situ conservation, the protection and propagation of orchids outside their natural habitat in places such as seed banks, laboratories, herbariums, and botanic gardens, have helped to preserve orchid species all over the world. This work includes the design of a botanic garden centred on orchids and their conservation. Situated in Ecuador, the garden design incorporates research, education, and conservation in a way that is inspiring and delightful to the visiting public. Orchids are featured in the design of the garden, and the conservation of this plant family is emphasized. A history of botanic gardens explores the evolution of this specific type of garden, providing a background for modern-day design. Case study analyses of contemporary botanic gardens provides additional information and insight into the changing role of botanic gardens in the 21st century. This Practicum explores the creation of an educational garden that is also entertaining and challenges the notion of what a botanic garden is today and what it can be in the future.

Thesis (Ph.D.)--Murdoch University, 2004. / Thesis submitted to the Division of Science and Engineering. Includes bibliographical references (p. 199-210).

Thesis (M. Phil.)--University of Hong Kong, 1997. / Includes bibliographical references (leaf 72-83).

Thesis (MScAgric)--University of Stellenbosch, 2005. / Bibliography. Also available via the Internet.