Fig. 1. Nomarski image of actively growing Allomyces arbuscula in liquid medium (YPSs) showing two oppositely growing poles. (A) General view of a young thallus representing two polarized cell types, hyphae (h) and rhizoids (r). (B) Rhizoidal pole. (C,D) Hyphal poles showing an apical exclusion zone containing a Spitzenkörper (s) and a sub-apical region containing nuclei (n) and mitochondria (m). Bar, 10 µm.