The influence of stem conformation on the crystallization of i-PP is studied by growing a-form lamellae in melts of beta-form lamellae at different temperatures. The melting of beta-form lamellae and the crystallization of a-form lamellae is observed in situ at the interface of alpha- and beta-form spherulites by AFM. The growth rate of beta-form lamellae in the melt of beta-form lamellae is much lower than that in the isotropic melt due to the stem conformation barrier, which originates from the difference in the alpha and beta unit cell packing models. (c) 2005 Elsevier Ltd. All rights reserved.