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The grass genera of the world: descriptions, illustrations, identification, and information retrieval; including synonyms, morphology, anatomy, physiology, phytochemistry, cytology, classification, pathogens, world and local distribution, and references |
This package is generated from a DELTA database (Dallwitz 1980; Dallwitz, Paine, and Zurcher 1993). It comprises an interactive identification and information retrieval system using the program Intkey, descriptions, illustrations, references, and other subsidiary material.
The original database contained detailed morphological, anatomical and physiological descriptions of over 800 grass genera (Watson and Dallwitz 1981; Watson, Dallwitz, and Johnston 1986; Watson 1987), incorporating extensive original observations. It has been updated (November 2016) to account for the worldwide phylogenetic classification of the Poaceae of Soreng et al. (2015), involving incorporation of over 50 additional genera recognised by them. We choose to retain numerous genera treated by them as synonyms, on the grounds that (a), many of them are likely to be resurrected by other taxonomists; (b), it is far easier to coalesce sensu stricto descriptions than to restore them by breaking down sensu lato versions; and (c), their retention better informs on sampling of important ‘esoteric characters’ such as anatomy, physiology, and pathogens. Because of sampling limitations, intrageneric variation in these characters may be underestimated. Sampling information is sometimes directly incorporated in the descriptions, but because of limitations on computer storage space in earlier times, species directly examined for leaf blade anatomy are listed in a separate file.
The interactive (Intkey) component is the main reason for preparing this package; so it is exasperating to find modern grass systematists routinely ignoring it and instead quoting from a hard copy book that was automatically generated from the Delta data in 1994. It is easy, using Intkey, to obtain lists of genera exhibiting or lacking particular features or combinations of features; to cross reference attributes with geographical distributions and taxonomic groupings; to compare the existing tribes and subfamilies with one another, and with proposed alternative groupings, in terms of the available descriptive data (with statistical details of character state distributions); to obtain lists of genera for which information on particular features is lacking; to locate generic synonyms; and to obtain printouts of all such information. The Soreng et al. classification is seriously deficient in lacking group descriptions, although these could easily have been prepared in detail from our readily available interactive package, by applying the ‘Summary’ option of Intkey (cf. our 1998 classification). For more information, see ‘Hints on using Intkey’ (accessible from the Intkey package), and published examples in Watson et al. (1989) and Bruhl et al. (1992).
Since 1977 we have tried, mainly via the Delta character list, to set a standard for preparing detailed, fully comparative taxon descriptions on grasses. Our descriptive terminology is mostly in line with normal agrostological usage, as set out in modern textbooks, monographs and regional floras, but has sometimes been modified and extended by us (e.g., Hubbard 1968, Hitchcock and Chase 1950, Gould 1968, Jacques-Félix 1962, Bor 1960, Clayton and Renvoize 1986, Chapman and Peat 1992, etc.; and for anatomy, Metcalfe 1960, Clifford and Watson 1976, Ellis 1976 and 1979, and Watson and Dallwitz 1988). In addition to morphology, anatomy, cytology and ecology, our character list and descriptions incorporate comparative data on other aspects of interest to research biologists in various disciplines; e.g., fungal pathogens, physiology, and pollen antigens and allergens. Detailed, written character notes have been entered for some of the characters, and the character illustrations should facilitate differentiating between character states. We emphasize that the original, comparative leaf-blade anatomical data in this package reflect examination by transmission light microscopy of adequate preparations of abaxial leaf blade epidermes and hand-cut transverse sections. Many of the epidermal characters, including some of physiological or ecological interest, are completely inaccessible or cannot be recorded reliably by scanning E.M.
We have tried to avoid copyright-restricted images, and have tried to ensure that all original sources are acknowledged in the Intkey displays, the HTML descriptions, and the References file. All images for which sources are not given can be assumed to have been prepared in Watson’s R.S.B.S Taxonomy Lab. Many images are derived from high resolution scans of plates from early taxonomic classics, mostly downloaded from the Biodiversity Heritage Library); notably line drawings from de Beauvois (1812), Kunth (1835) and the Hookers’ Icones Plantarum, as well as coloured plates from the Sowerhy et al. English Botany (1872 edition). These are historically fascinating and very rich in technical taxonomic details, but have required nomenclatural cross referencing, as well as editing of contents, revising of legends, and re-arranging image layouts to conserve space. We have also incorporated scans from Gardner’s (1952) account of Western Australian grasses, and from Grasses of Southern Africa (Gibbs Russell et al., 1990). There are scans of about 550 photos and line drawings, illustrating spikelet details and leaf anatomy, prepared in Watson’s R.S.B.S. Taxonomy Lab between 1972 and 1994, most of which have not been published elsewhere. Numerous photos of leaf blade sections prepared from herbarium material are included, because they often provide useful descriptive information.We also include photos of serological slides associated with an investigation of grass pollen allergens and antigens conducted in the Taxonomy Lab, many of which were not included in the related publications of Watson and Knox (q.v.).
The same suite of images is currently employed to illustrate both characters and taxa, with critical features ‘hot-spotted’. To locate ‘hotspots’, move the mouse cursor over text boxes or images. Character states are often illustrated by several images, to indicate the ranges of variation.
Our leaf blade anatomical preparations represent mid-laminar abaxial epidermis and hand cut transverse sections, stained with Phenolic Bismarck Brown as recommended by Clifford and Watson (1977). They mostly represent samples of leaves from authoritatively identified specimens provided by the Canberra and Royal Botanic Gardens, Kew Herbaria, whose contribution we gratefully acknowledge. The former Taxonomy Lab slide collection is now housed at the Western Australian Herbarium under the care of T.D. Macfarlane, along with the notebooks detailing information on the herbarium specimens sampled.
Revised 3 August 2019