The temperature dependence of the spherulitic growth rate of poly(butylene terephtharate) (PBT) has been investigated by optical microscopy and compared with the temperature dependence of the lamellar thickness. The changes in the dependence of the growth rate on the lamellar thickness are observed at three temperatures, 218, 208 and 157 degrees C. The middle temperature, 208 degrees C, corresponds to the temperature at which the temperature dependence of the lamellar thickness changes. The correspondence leads to the interpretation that the crystalline stem directly forms at the growth front above 208 degrees C and that the mesomoprhic stem forms below 208 degrees C. (C) 2017 Elsevier Ltd. All rights reserved.