In reviewing this monograph one is immediately faced with the fact that the only other account of this genus is by the same author, published 24 years ago, the much-valued Lachenalia Handbook published by the National Botanic Gardens in South Africa, now sadly out of print. This monograph thus encapsulates the pre-eminent expertise of the author, who is the specialist bulb horticulturist at Kirstenbosch National Botanic Garden and has studied this genus both in the wild and in cultivation. Not only this, almost uniquely these days for a horticulturist, he has been able to take his studies further and undertake detailed herbarium and scientific research, the findings of which are the core of this work. The result is a remarkable and satisfying combination of science and horticulture which is the hallmark of the Kew Botanical Monographs series.
The book begins with a series of chapters that provide a comprehensive introduction to the genus, covering the history, cultivation, conservation, ecology, morphology and cytology of the genus. Lachenalia, while not being the most well-known of cultivated plants, has a surprisingly long history in cultivation, with the first introductions to Europe in the second half of the eighteenth century. These were sumptuously illustrated in the various books by Nicolaus Jacquin which provide a record of the plants then growing at the Schönbrunn Palace in Vienna. These are rightly recognised in this monograph: indeed, the author has discovered some of the earliest names for Lachenalia species were published in Jacquin's overlooked works, which has implications for their naming as is shown in the taxonomic treatment. The various people who have made a significant contribution to the study of Lachenalia are noted, up to Winsome Fanny Barker who encouraged Graham Duncan's early interests in the genus: a debt he has repaid amply. It is clear that her skills extended beyond taxonomy, as the watercolour paintings by Barker included in this book, show.
The author outlines the history of hybridisation in Lachenalia, something which had challenged horticulturists for many years, especially before the significance of their chromosome numbers was understood. It is worth noting that there is only one hybrid recorded in the wild and that is between two species that were formally considered to belong in L. aloides. This is significant in that all the early hybrids (1870 up to the 1930s), were between taxa broadly considered to be L. aloides, including L. × nelsonii, widely referred to in cultivation as the cultivar L. ‘Nelsonii’, but for which the hybrid epithet is revived as a result of the author's treatment of L. aloides sensu lato. In this section there is a charming portrait of the young Charles Darwin holding what is undoubtedly a Lachenalia, grown presumably by his botanically inclined grandfather, Erasmus, and which Graham Duncan names L. × nelsonii. The painting is dated to approximately 1816, some sixty years before the date when the hybrid was raised. It seems far more likely that the plant in question is a species in the L. aloides group which had begun to be introduced to the UK by 1774.
As is so often the case with South African plants, the section on conservation highlights the plight of so many species that are narrow endemics and therefore threatened by habitat change and development. That is balanced by some striking photographs of lachenalias growing in the wild en masse. Also worth noting is Table 2, giving the flowering times for all species of Lachenalia, which is particularly useful to those cultivating them, although it needs to be remembered by those in the Northern Hemisphere that for June read December, and so on. The chapter on biology gives a resume of the taxonomic characters of the genus, both macro- and micromorphological. It reveals a thorough study of all aspects of the plant, although at times it seems there is a plethora of terms, but there is a useful glossary at the end of the book to help with this. And while there is plenty of information about the flowers, I would have liked to have seen discussion about the gibbosities on the perianth segments, which are distinctive, and may have a role in pollination. When the author returns to more ecological aspects, such as pollination, there is much valuable information, backed as it is by observations he has made. The evidence for this is in the magnificent photographs of pollinators in action.
The morphological study provided the basis for the author's cladistic analysis of the genus. This is covered in a relatively brief chapter on phylogeny which refers to an earlier publication, where the phylogenetic trees were published (Duncan et al., 2005). While there was no molecular component of the phylogenetic analysis, the author draws attention to the sequencing work by Spies (2004) and acknowledges that further work is needed to clarify some of the poor resolution in the trees. It is curious that the informal groups proposed by Spies (2004) do not match the infrageneric taxa proposed in this work.
Included in the genus are the species which formerly belonged in Polyxena, reduced to synonymy with Lachenalia by Manning et al. (2004), now given subgenus status in this work. Although species of Polyxena appear quite distinct from Lachenalia, the trees published by Manning et al., show them to be embedded within Lachenalia. While recognising Polyxena as a subgenus renders subgenus Lachenalia paraphyletic, it should be appreciated that the disappearance of Polyxena at any level would be an unwelcome change for many users. In the monograph the subgenus Lachenalia is divided into five sections, all defined in the key on floral characteristics. While this makes for an effective diagnostic tool, one wonders how phylogenetically natural the sections are, given how evolutionarily labile floral characters are.
The present work has accounts of 133 species, of which ten are new species described in the monograph. The Lachenalia Handbook includes 88 species: it was not comprehensive, as the author admitted at the time that there were some species that had been described but were too poorly known to be covered. Since then some 36 new species have been described, many by Graham Duncan, a remarkable indication of the unwarranted neglect and the hidden diversity of Lachenalia. In addition to the new species (and new subspecies), there are 12 nomenclatural novelties, mainly where the author has elevated infraspecific taxa to species level. One of these turns out to be illegitimate as a later homonym. Lachenalia bulbifera (Cirillo) Engl. (1899) is replaced by L. bifolia (Burm. f.) W.F.Barker ex G.D.Duncan, based on Aletris bifolia Burm. f. (1768). This would be correct, as Cirillo's name was published in 1788, were it not for the existence of Lachenalia bifolia Ker Gawl. (1814), as noted by the author. While this is a later date of publication than Burman's species, the latter cannot displace the former, as it is the earliest valid publication of the name in Lachenalia, even though it is not currently an accepted name for a species. This is covered in Article 11.4(b) of the ICN, see also Example 12 (McNeill et al., 2012).
The major part of the monograph is the taxonomic account of the 133 species. First, and probably most importantly, this includes a key to the taxa, invaluable as until now there has been no comprehensive modern key. Each species has a full synonymy, detailed description, historical account, distinguishing characteristics, distribution – with a map provided for each, habitat and conservation status information. This is combined with excellent photographs and, for some, paintings. By and large the species are those accepted in the Lachenalia Handbook or as published subsequently, except for three species groups: the L. aloides group, the L. elegans group and the L. unifolia group. These taxa formerly contained varieties which Graham Duncan has elevated to species, most notably in the L. aloides group. In this group his differentiation of species has, apart from flower colour, depended upon measurements of the flower parts. While this is not an unreasonable approach, it would be more convincing, given the overlap in measurements between species, if there was evidence of a more rigorous statistical analysis, perhaps using relative proportions. Given, also, the detailed morphological study described in the introductory chapters, it would have been helpful to know if any non-floral characters could be used to support the recognition of the new species. That said, there are clear distributional differences and it is well known that in the Cape floral region, there is a rich diversity of species over a relatively small area.
The book is well illustrated throughout with a combination of line drawings, paintings and photographs. There are 39 plates of paintings by nine different artists; the majority are, however, by the author's acknowledged mentor W. F. Barker. The paintings are of exceptionally high standard and reflect a variety of styles of representing the plants. The photographs are mainly those of the author and are of Lachenalia both in the wild and in cultivation. It is a considerable accomplishment that every species is illustrated with high quality photographs – some are incredibly rare and others, such as the pyrophytic species, really difficult to flower.
In addition to a bibliography, a general index and index to scientific names, there is a helpful glossary providing definitions for such unusual terms as gibbosity, nototribic and proteranthous, as well as many of the better known ones.
Graham Duncan's earlier Lachenalia Handbook can reasonably said to have rekindled interest in the genus over the past 20 years: I have no doubt that this fine monograph will stimulate a much broader appetite to know and grow members of this surprisingly diverse genus. The price of the book may well deter, but nowhere else will you find such a combination of photographs, paintings, detailed descriptions, a key, distribution and cultivation information, written by the one person who knows the genus like no-one else. This is a book to use and to treasure.