excellent cell biology hormone and light signaling pathways operative few cell types & simple developmental pattern polar tip growth and division tolerant to water stress A Model System for Functional Studies draft genome assembled* gene targeting & RNAi gene id from 2-d gels 4x44 Agilent microarray gene id by genetic map position insertion and deletion libraries Quatrano, R. S., et al. (2007). Current Opinion in Plant Biology 10: *Rensing, et al. (2008). Science 319: Physcomitrella patens Haploid, single-cell layer, leaf-like gametophores of P. patens