1997 Volume 82 Pages 245-251
The occurrence of stomates in bryophytes and tracheophytes is briefly reviewed. It is argued that the stomate is not a simple structure and that it could not evolve by simple processes. The schizogenous nature of the stomatiferous internal air system is emphasized, and the occurrence is noted of stomates in gametophytes as well as sporophytes of early land plants. It is considered possible that the internal air systems of Marchantialean Hepaticae and the stomatiferous systems of other land plants have a common evolutionary origin.