Liliaceous ornamental plant Muscari armeniacum Leichtl. ex Bak., generally called 'muscari' or 'grape hyacinths', is cultivated for pot or garden uses throughout the temperate regions of the world. This bulbous plant has several attractive traits such as blue flower color and vigorous growth, which are desired to be incorporated via somatic hybridization into the other Liliaceous ornamental plants. In order to apply somatic hybridization for genetic improvement, establishment of a protoplast culture system is prerequisite. Although plant regeneration from protoplasts has so far been reported for several Liliaceous ornamental plants such as Agapanthus praecox ssp. orientalis (Nakano et al. 2003), Lilium spp. (Mii et al. 1994; Godo et al. 1996; Horita et al. 2002) and Hemerocallis hybrida (Fitter and Krikorian 1981), no studies on protoplast culture have yet been reported for M. armeniacum. In the present study, we describe for the first time plantlet regeneration from protoplasts of M. armeniacum. Leaf-derived embryogenic calluses of M. armeniacum 'Blue Pearl' (Suzuki and Nakano 2001; Mori and Nakano 2004) were used as a protoplast source. Before protoplast isolation, the calluses had been maintained for 3 years by monthly subculturing onto half-strength MS medium (Murashige and Skoog 1962) containing 54 m M NAA, 30 g l Ϫ1 sucrose and 2 g l Ϫ1 gellan gum. All media used in the present study were adjusted to pH 5.6-5.8 prior to autoclaving at 121°C for 15 min. For isolating protoplasts, 1 g fresh weight of the calluses 2-4

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This study investigates the determinants of cocoon prices under trade contracts that prevailed during the inter-war period in Japan between silk-reeling companies and cocoon farmer cooperatives (Tokuyaku Torihiki). The contract documents show that the process of cocoon price agreements incentivized the cooperative and its member farmers to improve cocoon quality and to reduce the risk of cocoon prices. However, the results of the estimated price determinants did not support these predictions.