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Single-phylogram scenario illustrating key land plant lineages (bold text) and moss genera and the appearance of stomata in modern plants. Dashed lines indicate absence of stomata and solid black lines their presence. This phylogram with liverworts basal (Qiu et al., 2006, 2007; Liu et al., 2014) indicates a single origin of stomata and multiple losses, whereas an alternative topology with hornworts basal implies multiple origins (Haig, 2013; Wickett et al., 2014).
