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The Families of Flowering Plants |
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This package is generated from a DELTA database (Dallwitz 1980; Dallwitz, Paine, and Zurcher 1993). It comprises an interactive system for identification and information retrieval using the program Intkey (Dallwitz, Paine, and Zurcher 1995, 2000) (running under MS-Windows 95/NT or later), descriptions, illustrations, references, and other subsidiary material.
The reasons for preparing these automated descriptions of Angiosperm families, the intended applications for which the database was designed, and the rationale for the manner of its construction, were set out in detail when it was first released (Watson and Dallwitz 1991).
The set of descriptions is ‘complete’, in the sense that it purports to include all the families, and to carry for each of them a morphological description that is at least workable for identification. Some of these are minimal even for that purpose, and there is infinite scope for improvement. However, comprehensive information is included on geographical distributions, on variation in photosynthetic pathways (with lists of the genera known to include C4 and/or CAM species), and on the occurrence of leaf phloem transfer cells (the latter summarizing primary data not published elsewhere). Very extensive data are also included on other features, including seedling germination type, embryology, anther ontogeny, pollen cytology and morphology, stigma type, sieve-tube plastids, leaf, stem, nodal and wood anatomy, and phytochemistry (phenolics, alkaloids, cyanogenesis, etc.). Also included are family synonyms; comprehensive information on numbers of species and genera in each family, and complete lists of the genera in each; the complete classifications, to the level of Order, of Dahlgren (1980), Cronquist (1981) and Takhtajan (1980) for Dicots, and of Dahlgren, Clifford and Yeo (1985) for Monocots; and comprehensive assignment of Dicotyledons to the major groups Crassinucelli and Tenuinucelli of Young and Watson (1970), which represent the clearest and most useful high-level taxonomic distinction yet demonstrated in that assemblage (the Cronquist and Takhtajan subclasses are unsound, and Dahlgren’s 18 superorders, while taxonomically far superior, are too numerous to satisfy the routine sampling requirements of experimentalists). DNA sequencing studies from 1993 onwards are providing important new phylogenetic and classificatory insights, and we include here the APG (1998) classification of Flowering Plants into purportedly monophyletic ordinal and supra-ordinal groups, to facilitate cross referencing this with the existing, comprehensive taxonomic treatments. It is not yet practicable to present an up-to-date, detailed classification, given the incompleteness of nucleic acid sequence studies and the mainly piecemeal and sometimes contradictory results obtained thus far from a plethora of other cladistic analyses. In many cases the need for reassignments is indicated in the descriptions given here, however, and sometimes these have been made within the framework of the Dahlgen and Dahlgren et al. systems.
Narrow family circumscriptions, mainly as exemplified by Airy Shaw (1973), are deliberately employed here. These are in general preferable in the present context both to the broader interpretations of Cronquist (1988; see also Mabberley 1989) and to those now being proposed with increasing frequency (and sometimes with shallow justification) on cladistic grounds. The elevated levels of internal variation exhibited by overlapping, sensu lato descriptions preclude effective family diagnoses, are unpractical for pursuing identifications, and pose serious problems for classificatory and cladistic analyses of the data. A further advantage of narrowly circumscribed families in the present context is that they better indicate the extent of sampling in relation to ‘esoteric’ characters, many of which are of considerable taxonomic and/or economic importance. Should sensu lato descriptions be wanted, they are easily generated automatically from the sensu stricto versions using Intkey.
Many of the works listed in the references are largely or partly compilations, which themselves cite primary data sources: the latter are listed only when they have been utilized directly. The character (q.v.) list includes some provisional characters and suites of ‘characters’, which have yet to be resolved into satisfactory characters and states. For example, an obviously unsatisfactory ‘character’ was used to assemble descriptive information on styles, stigmas and stigmatic surfaces in apocarpous and syncarpous gynoecia. This and similar cases could be resolved later, when proper assessments of the available descriptive data have been made. For information on individual characters, consult the notes on individual characters available via Intkey.
The package includes extensive illustrations of both taxa and characters. The numerous line drawings are mainly from Le Maout and Decaisne’s A General System of Botany (1873: illustrated by L. Steinheil and A. Riocreux, who used Decaisne’s collection of analytical drawings), Lindley’s The Vegetable Kingdom (1853: illustrations specially prepared for that work, or from other sources specified on the legends), and Thonner’s Flowering Plants of Africa (1915). The layouts have been changed, mainly to account for family realignments, and some effort was required to remove foxing and fingerprints. It has seemed inappropriate to replace the original legends, although it should be noted that they sometimes carry superseded generic names. The 400+ high resolution coloured illustrations, incorporated recently, mainly represent scans of hand-coloured engravings from J. Curtis’s British Entomology (1824–1835).
The same suite of images is currently employed to illustrate both taxa and characters, with critical features ‘hotspotted’ in the interactive identificatory context. Many character states are exemplified by several images, in an attempt to indicate the ranges of variation they encompass; and numerous families are represented by several taxon images.
Buttons in the Intkey toolbars permit selecting subsets of characters and taxa for efficient pursuit of specialised identificatory problems (geographical subsets, fragmentary material, fossils, etc.). It is also easy, using Intkey, to obtain lists of families exhibiting or lacking particular features or combinations of features; to cross reference attributes with geographical distributions and classifications; to compare rival family classifications in terms of group contents, and in terms of the available descriptive data (with statistical details of character state distributions); to obtain lists of families for which information on particular features is lacking; to locate family synonyms, and assign generic names to families; and to obtain printouts of all such information.
In addition to the Intkey package, the full family descriptions are available (with diagnostic attributes highlighted) on the World Wide Web (WWW) (Watson and Dallwitz 1992).
