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This account of chromosome variation in the Commelinaceae is based both on the authors' personal experience with a very large living collection of the family at Kew, and on the numerous reports of earlier workers. There can be few families showing such a wide range of chromosome numbers, karyotype morphology and meiotic behaviour, the description of which may be of interest to cytologists, evolutionists and taxonomists alike. In this present survey the information is presented within the framework of a tentative classification of genera proposed by Brenan, and comments are made throughout on the relevance of cytology to his taxonomic treatment of the family. It is hoped that this account will foster further interest in the Commelinaceae, and in particular, encourage more thorough appraisal of intraspecific chromosome variation and interspecific homologies.

Purpose -This paper aims to draw attention to the weakness inherent in the current theoretical model underpinning built asset maintenance and to propose a new performance based model that aligns maintenance/refurbishment expenditure to corporate performance. Design/methodology/approach -An action research approach was used in which participants from within a commercial organisation worked with the research team to develop a new theoretical approach to built asset maintenance. A series of meetings, workshops and interviews were used to: evaluate the organisation's approach to built asset maintenance; identify opportunities for improvement; and develop a new conceptual model of their built asset maintenance process. The logic underpinning the conceptual model was tested through a series of presentations to the organisation's middle and senior management. Findings -The current theoretical model underpinning built asset maintenance does not allow direct links to be drawn between expenditure and impact on business performance. The new approach forces facilities managers to consider the business implications of their actions before large maintenance programmes are developed and provides feedback mechanisms to monitor the impact of any actions against key business drivers. Research limitations/implications -At this stage the new performance model is still theoretical and requires implementation to test its robustness and resilience. Practical implications -The adoption of the model will force facilities managers to consider the implications of their maintenance/refurbishment actions at a strategic level, thus placing their considerations on a similar footing to their human resource and financial counterparts. Originality/value -This paper extends the performance based concept to built asset maintenance and provides a practical process model through which the concept can be implemented.

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With Plate 3 and 6 figures in the text) SUMMARY Studies have been made of the relative frequency and distribution in parts of Britain of the chromosome races oi Holcus mollis {zn = 28, 35, 42, 49). These show that the pentaploid is the most common race and that the distribution of the races as a whole is a reflection of varying degrees of adaptability to moisture content of the soil.Chromosome studies at meiosis and mitosis show that the tetraploid is an allopolyploid and that the hexaploid is derived from it. The pentaploid appears to be derived from a hybrid of H. lanatus {zn =14) and H. mollis {2n = 28).The hybrid nature of the pentaploid is confirmed by the discovery of natural triploid hybrids (2« = 21) from which it is presumed to have been derived by backcrossing to the tetraploid parent.With the exception of the tetraploid, the races of H. mollis reproduce almost exclusively by vegetative means. The tetraploid is fertile but is also likely to reproduce mainly by rhizomes.The success of the pentaploid is attributed to its hybrid vigour in both growth and adaptability to soil moisture. In addition its spread is favoured by the fact that its tetraploid parent does not offer much seed competition in the colonization of new areas. There is no competition from the H. lanatus parent which has different ecological requirements.It is considered feasible that the vigorous pentaploid could eventually supersede the other races of H. mollis.

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