The variation in floristic composition and physiognomy of the so-called grass-heath of Breckland (East Anglia) is causally related to a series of soil stages in the development of a podsol beginning with a highly calcareous shallow soil. Text figures show the profiles of CaCO3, pH, "sequioxides" and carbon and data of the CaCO3, pH, exchangeable Ca and total bases, C and N of the surface soil reveal a marked gradient of fertility. 5 major steps in the series and 2 minor (variations of the last) are recognized. Full lists of spp. of vascular plants, bryophytes and lichens of 7 communities are given. The flora is drought-resistant and drought-evading and is grouped on the basis of soil requirements into calcicole, exacting, calcifuge and tolerant species. Arranged in arrays the shift of the focal points of these groups is obviously correlated with soil change spp. with narrow ecological requirements are highly diagnostic. From a maximum in the 2d stage the number of species falls on either side to a very low number on the most podsolized soil, this being due to the fractional elimination of spp. with soil change and not to a radical change in the flora: thus the species tolerant of a wide range of soils dominate on the podsol; typical calcifuges are scarce.