Maslova, E.V., Yu.V. Mosseichik, I.A. Ignatiev, O.V.
Ivanov & M.S. Ignatov. On the leaf development in Palaeozoic mosses of the
Arctoa (2012) 21: 241-264
mosses of the order Protosphagnales are studied for their leaf development and
found to be quite different from modern mosses. In the latter, the small
actively dividing cells occur at latest stages of leaf development in the
proximal part of leaf, whereas in Protosphagnales cell divisions may continue
in the subapical part of leaf. Also, zones of small cells occur in some genera
in the median part of the leaf, indicating relatively independent development
of different leaf parts. The narrow insertion of leaves, which consists almost
entirely of the costa, makes easier late growth of the basal leaf portion,
where expanded aurucules may form. The small cells in median part of leaf
differentiate both acropetally and basipetally, but cells above this zone
become dimorphous more often than below it. The pattern of cell dimorphism is
correlated with shifts of cell rows during leaf development.