Christopher D.K. Cook’s research while affiliated with University of Zurich and other places

Cook, C. D. K. & Rutishauser, R.: Name changes in Podostemaceae. – Taxon 50: 1163–1167. 2001.‐ISSN 0040–0262. While preparing a review of the family Podostemaceae , we have found it necessary to change the name of some species. Following rules of priority, Crenias K. P. J. Sprengel replaces Mniopsis Martius. No convincing reasons can be found to maintain the monotypic genera Hydrobryopsis, Malaccotristicha, Synstylis and Torrenticola ; they are merged in their sister genera Zeylanidium, Tristicha, Hydrobryum and Cladopus , respectively. On morphological grounds Polypleurella micranthera is transferred to Hydrobryum and Polypleurum submersa is transferred to Saxicolella.

The extant embryo-bearing plants (mosses, ferns and seed plants) have an aquatic ancestor or ancestors. Today they dominate the terrestrial vegetation of the world. Embryo-bearing plants which now live in water have, for a second or even third time, re-invaded water. Aquatic species are found in 440 genera from 103 families of embryo-bearing plants. This survey attempts to find out how often the Event of evolving from land back to water has taken place among the living plants of today. Analysing the morphological and phylogenetic affinities of all aquatics at taxonomic levels from divisio to varieties of species indicate the Event has taken place, at least 222 times but it could have happened 271 or even more times (bryophytes 10–19 times, ferns seven times, seed plants 205–245 times). Aquatic plants have evolved from often very different genetic and ecological backgrounds. Also, they have evolved at different times; some old ones are aquatic at the level of order or family, while others, more recent, are isolated species in otherwise terrestrial genera or races within species. It is, nevertheless, wonderful that such a large variety of plants have evolved solutions to the single problem of remastering life in water.

Cook, C. D. K.: A quick method for making accurate botanical illustrations. – Taxon 47: 371‐380.1998. – ISSN 0040‐0262. Not all botanists in need of illustrating their publications are gifted artists, and trained as such; nor can every botanist or publisher afford hiring professional help. To those who decide to produce their own drawings, this paper gives practical guidance of how to proceed, illustrated by examples of how palatable the results may look.

Wiesneria triandra (Dalzell) Micheli is a phylogenetically isolated, local, endemic species of southwest India. It is annual and very sporadic in occurrence but when it is found it is often locally abundant. The inflorescences have mostly unisexual flowers with females borne below the males. Experiments have shown W. triandra to be amphimictic and self-compatible. Pollination can take place without a biotic vector. It is likely that it is highly inbreeding in spite of having unisexual flowers. The nutlets are very hard and have lateral gas-filled invaginations which provide short-lived buoyancy. The seeds have a dormancy induced by the testa (or perhaps the pericarp) which can be broken by mechanical, physical and chemical scarification. Dormancy is an important survival strategy, preventing seeds from germinating after showers during the dry season. The nutlets are dispersed over short distances by water. A mechanism for dispersal over long distances is unknown; the nutlets are digested by Anas platyrhynchos L. and are unlikely to be carried externally on water birds because they are hydrophobic, globose and rather heavy. Germination is typical for the family (with ‘Haarkranz’ and suppressed primary root) except that the hypocotyl emerges through a clearly demarcated cap. Plants growing in and out of water show a marked heteroblastic leaf development, the ‘juvenile’ leaves are strap-shaped while the ‘mature’ leaves are clearly differentiated into petiole and blade. In 1993 we were able to study two populations. Although the two populations were about 160 km apart, no convincing inter- or intra-population variation was detected using morphological characters and eight isozyme systems. Today, W. triandra is found only in habitats modified or maintained by man; the original habitat is discussed. Although rare it is not threatened with immediate extinction but is very susceptible to change in land usage and should be placed in the ‘vulnerable’ category.

This volume is a reference and identification manual for the vascular plants found in permanent or seasonal fresh water in the subcontinent of India south of the Himalayas. About 660 species are described and the style of the text is accessible both to experts and to those with only a little botanical training. All the plants are illustrated by line drawings showing the diagnostic features. The importance of wetlands to life on Earth is now generally accepted. This is the first such Flora to cover wetland plants for this entire geographical area, replacing and supplementing many local Floras. It will enable scientists and conservationists to identify the plants with accuracy and to build on this information to promote conservation. This is a most valuable contribution to systematic botany by an international recognized scientist.