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Gulture medium composition is critical for the successful induetion of microspore division tn vitro.The present experiments have focused on a relatively neglected area of cell and tissue culture research, namely the carbohydrate eomponent used in the medium. Three spring barley genotypes were cultured on a medium whieh was modified by replacing sucrose with the following carbohydrates (6 % w/v): maltose, fructose, malt extract, galactose and a glucose (3 % w/v)/fructose (3 % w/v) mixture. Both maltose and malt extract were superior to sucrose in their capacity to induce green plantlet differentiation from microspores. The concentrations of both suerose and maltose were also varied. Overall the response of anthers on maltose based tnedia was higher than on sucrose based media, [furthermore, a eoncentration of maltose in the range 6-12 % w/v produced a higher frequeney of green plants than a low concentration (1-3 % w/v). The effect of maltose based media on germplasm of direct relevance to barley breeders was also tested. The cultivar 'Blenheim' was shown to be very responsive and this genetic factor was transmitted to the Fi hybrid. The frequency of haploid to diploid regenerants was not eonsistent over genotypes, but in general there were more haploid than diploid regenerants. The implications of these results for barley breeding are discussed.

Some fern species form spore banks -reservoirs in the soil of viable spores which remain dormant while buried but germinate in light if brought to the surface. The recently discovered characteristics of these spore banks are described. Enough is now known to suggest that they might have a role in the conservation of endangered fern species as alternatives to ex situ collections of sporophytes, gametophytes and spores, the relative merits of which are also considered. Mature sporophytes of several British species have now been raised from natural spore banks in soil samples; if this proves to be possible also for endangered species, some interesting options become available. The possibilities are discussed of augmenting surviving populations and increasing their genetic diversity, even perhaps of retrieving lost populations, by reintroduction of spore bankderived plants or by stimulating regeneration from spore banks in situ. Botanic gardens are well placed to provide the further research, the regular monitoring of endangered populations, and the taxonomic and horticultural support required to realise these possibilities.

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