The "two inversions" model for IR rearrangements in fern cp genomes. Genes are represented by boxes extending above or below the base-line according to the direction of transcription. The genes that are absent in the Alsophila cp genomes are shown in purple: these loci are merely hypothetical in putative intermediates since the course of their loss is unclear. The pseudogene of trnT-UGU is represented in red and indicated by ψ. The tRNA anti-codon is abbreviated in putative intermediates.