Also, the existence of sharp boundaries between habitats in nature (as at
the edge of a steep-sided lake) may lead to "communities" being apparently
more discrete. Many modem systems of vegetation classification, such as
that devised by [ohn Rodwell for the description of the vegetation types of
Britain [2], are based on the idea of frequently repeated combinations being
selected and described, which can then be used as reference points. This
type of scheme allows the possibility of a wide rangeof intermediate types,
which is what one would expect if Gleason's ideas are valid.