Timmia bavarica

Timmia bavarica ( Fig. 7 View Fig )

The studied sequence of divisions results in pattern characterised by the following formulae: 2:1(not shown) — 2:2:1 — 4:2:2 — 8:4:4:4 (opposite). The IPL:PPL cells thickness ratio is 1.5–2:1. Repeated anticlinal divisions occur at later stages of development in both IPL and PPL ( Fig. 7D, E, G View Fig ). Cells of peristomial layers, as seen in longitudinal sections ( Fig. 7C View Fig ), are more regularly arranged compared to Encalypta ( Figs. 2C View Fig , 3A View Fig ).

Funaria arctica ( Figs. 8, 9 View Fig )

As the genus Funaria has been already a subject of the peristome development studies, we display here mostly the later stages. Fig. 8A View Fig shows the stage where some IPL cells are already underwent anticlinal divisions (corresponding to 4:2:4 formula), while some did not, thus fitting 4:2:2 formula, which is characteristic for earlier stage of development. IPL cells have divided periclinally at the level reached by sporogeneous tissue: darker cell content in the outermost endothecial layer is not yet discernible in Fig. 8D View Fig , but becomes more or less apparent 10 µm below, at Fig. 8E, F View Fig , and clearly seen further below, at Figs. 8G, H View Fig . Note that the regular pattern of peristomial layers is still distinct at the level of urn, where sporogeneous tissue is apparent ( Figs. 8, 9 View Fig ).

For the present study it is important to note that Funaria differs from Encalypta and Timmia by a relatively better developed PPL, so the IPL:PPL cells thickness ratio is 0.8–1(–1.3):1; the anticlinal divisions in PPL are absent, and cell walls in neighboring peristomial layers are always clearly aligned.