An understanding of the evolution of roots based on fossil evidence is only being obtained slowly. This fossil evidence does not support a monophyletic origin of roots in polysporangiophytes. Molecular genetic studies on root development in extant lycophytes and euphyllophytes (including seed plants) should give further information on this point.
Work in JAR's laboratory on roots has been, and/or is, supported by AFRC, BBSRC and NERC, and DE's research on early land plants by NERC. Comments from Dr KR Skene and Dr W Bruce, and by Professor WG Chaloner and another, anonymous, referee have been very helpful.
3 To whom correspondence should be addressed. Fax: +44 1382 344275. E-mail: [email protected]