Phytochrome evolution: Phytochrome genes in ferns and mosses. -Physiol. Plant. 91: 241-250.We have isolated phytochrom'e genes from the moss Physcomitrella, the fern Psilotum and PCR-generated phytochrome sequences from a few other ferns. The phytochrome gene of the moss Physcomitretla tumed out not to contain the aberrant C-terminal third of the phytochrome from the moss Ceratodon, but the transmitter module-like sequences fonnd in other phytochromes. A series of differeni phytochrome genes was detected in Psilotum, Differences between the amino acid sequences derived from them ranged from about 5 to more than 22%. Some of these genes are likely pseudogenes. Analysis by phylogenetic tree constructions revealed that higher and lower plant phytocbromes evolved with different velocities. Lower plant phytochromes form a sepai'ote family characterized by a high degree of similarity. The amino acid differences bettt'een phytochrome types detected in a single species of higher plants are about two-fold higher than the differences between phylochromes ' Of species of lower plants belonging to different 'divisions (Physcomitrella and Selaginelki), Future studies on phytochrome sequences may eventually also throw light on the significance of P.'iilotum in the evolution of vascular plants.