Below is a list of fern (Pteridophyta) families, and the genera which are placed in them, using the classification scheme proposed by Smith et al. (2006), placed in the linear order of Christenhusz et al. (2011). Note that Smith et al. (2006) used the more traditional classes as listed below, while Christenhusz et al. (2011) used the corresponding subclasses (shown in square brackets) proposed by Chase and Reveal in 2009. In their proposal, all land plants (embryophytes) are placed in a single class, Equisetopsida, and the ferns (monilophytes) are assigned five of the 14 Equisetopsida subclasses. However, Christenhusz et al. merged the Psilotidae into the Ophioglossidae subclass, leaving four fern subclasses, corresponding to the four classes of Smith et al.