The following four papers are synopses of ones delivered in connection with the Annual General Meeting of the Society held at Monks Wood Experimental Station, Abbots Ripton, Huntmgdon on 29th April, 1967. BETULA L. IN BRITAIN
Three species of Betula are native in Britain. One of these, the Dwarf Birch, Betula nana L., is almost restricted to Central and North Scotland, and is very distinct in its dwarf habit (and in other characters of leaf-shape and inflor-escence); although hybrids occur locally with B. pubescens, it n...
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| Language: | English |
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.665.6162 http://archive.bsbi.org.uk/Proc7p179.pdf |
| Summary: | Three species of Betula are native in Britain. One of these, the Dwarf Birch, Betula nana L., is almost restricted to Central and North Scotland, and is very distinct in its dwarf habit (and in other characters of leaf-shape and inflor-escence); although hybrids occur locally with B. pubescens, it normally causes no taxonomic difficulty. The tree Birches, however, constitute a difficult taxo-nomic group which can only be understood on a world scale, and with cyto-genetic, experimental study. To some extent we can be said to understand the broad outline of the picture. It is possible to distinguish generally in Europe between a diploid species B. pendula Roth (B. verrucosa Ehrh.) with 2n = 28, and a tetraploid aggregate (2n = 56), for which the name B. pubescens Ehrh. is best used. 'Pure ' B. pendula is a tree up to 30 m, with slender, pendent, glabrous twigs beset with resin-glands, smooth silvery-white bark, dark bole with rectangular bosses, subglabrous biserrate leaves and a set of characters of fruit and catkin-scale. 'Pure ' B. pubescens subsp. pubescens is a shrub or small tree up to 20 m with hairy, eglandular twigs |
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