Summary Stace, C. A.: Cytology and cytogenetics as a fundamental taxonomic resource for the 20th and 21st centuries. ‐ Taxon 49: 451–477. 2000. ‐ ISSN 0040‐0262. The status of cytological and cytogenetic data as evidence of value in taxonomic decisionmaking and biosystematic investigations over the past 50 years is surveyed. The main headings considered are chromosome number, genome size, chromosome morphology, chromosome staining characteristics, chromosome and genome disposition in the cell, and chromosome behaviour and homology. The main conclusions are that many of the exciting new developments at the borders of cytogenetics and molecular biology (molecular cytogenetics) are producing a wealth of new data of enormous taxonomic and evolutionary importance, but that for these to reach their full impact it is essential that they are fully integrated with traditional cytological data, the need for which remains as great as ever.

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1991. A new taxonomic treatment of the Festuca ovinu L. aggregate (Poaceae) in the British Isles. A wide range of morphological, anatomical and cytological characters was collected and analysed by a variety of methods, some taxometric. As a result nine species are recognized in the British Isles, one (F. glauca Vill.) only as a garden plant and two (F. huonii Auquier and F. armoricana Kerguden) only in the Channel Isles. Two other species sometimes claimed for the British Isles (F. guesvalica Boenn. ex Reichb. and F. indigesta Boiss.) are excluded for various reasons given. One species (F. ovina L.) is divided into three subspecies: the diploid subsp. ouina (commonest in the north); and the tetraploid subsp. hirtula (Hackel ex Travis) M. Wilkinson (the commonest taxon of the aggregate in the British Isles) and subsp. ophioliticola (KerguClen) M. Wilkinson (scattered throughout the British Isles, but commonest on chalk and limestone and not restricted to serpentine soils as once thought).

Loliinae (Poaceae, Pooideae) encompass a large group of genera closely related to Festuca, the largest genus in the subtribe, which as traditionally circumscribed has been shown to be highly paraphyletic. In this investigation we combined molecular and morphological data representing 20 genera of Loliinae and closely related subtribes. Combined analysis of nucleotide sequences from the nuclear ITS and chloroplast trnL-F regions and structural characters recovered a consensus topology that shows Loliinae to be monophyletic and possessing two main clades-the fine-leaved Festuca clade that includes Ctenopsis, Micropyrum, Narduroides, Psilurus, Vulpia, and Wangenheimia, and the broad-leaved Festuca clade that includes Lolium and Micropyropsis. The presence of morphologically intermediate, unresolved, or poorly supported taxa (Castellia, Festuca subgen. Subulatae and subgen. Leucopoa p. p., and Festuca sect. Amphigenes p. p.) among the two groups points to a potential evolutionary trend from ancestral broad-leaved taxa to the more recently evolved fine-leaved taxa. Alternate classifications are evaluated for subtribes Loliinae, Cynosurinae, Dactylidinae, and Parapholiinae. We propose to maintain a paraphyletic Festuca as presently circumscribed and not to divide the polyphyletic Vulpia and Festuca infrageneric taxa until more phylogenetic data become available.

Results of hybridisation experiments involving five perennial European species of Brachypodium (B. sylvaticum, B. glaucovirens, B. pinnatum, B. phoenicoides and B. retusum), the annual B. distachyon, and the C. American perennial B. mexicanum are presented. Four of the European perennials are largely self‐incompatible, whereas B. sylvaticum, B. distachyon and B. mexicanum are highly self‐compatible. Despite their avowed ancient and relict status, the European species have mostly retained the ability to interbreed and produce viable F1 hybrids. The F1 hybrids obtained between the five European perennials all exhibit some degree of fertility. Hybrids between B. distachyon and at least some of the European perennials are vigorous and long‐lived, but show no evidence of fertility. No hybrids involving B. mexicanum could be raised. Success in raising hybrids, and the degree of fertility of such hybrids, partly agrees with closeness of taxonomic relationships as measured by morphological, anatomical, biochemical and molecular characteristics, but also with closeness in chromosome number irrespective of taxonomic affinity. Hence some interspecific hybrids are more easily produced and are more fertile than certain intraspecific hybrids involving parents of different chromosome number. All hybrids form good numbers of bivalents, but meiosis varies from almost regular in hybrids between European perennials with the same chromosome number to very irregular in hybrids between B. distachyon and any perennial species.