No CrossRef data available.
Published online by Cambridge University Press: 11 June 2012
A system of twelve stages of expansion from one primary monotypic genus is described and elaborated, using as two correlated parameters the rate of x 1·5 for the number of new monotypic genera arising (rGi) when the rate of X 2·0 is taken for the increase in generic size or numbers of species within any one genus (rSz). Too much stress should not be read into the precision of the positions indicated for known numerical data; an approximate fitting is all that can be reasonably expected even if these theoretical expansions are something like the historical truth.