Perichaetial module basal

FIGURE 14.5 Architecture of pleurocarpous mosses characters 11 to 12 (perichaetial module origin and sub-perichaetial innovations). (A) Perichaetial modnles formed distaUy on primary modnles and on secondary modules, subperichaetial innovations absent (Pireella) (B) perichaetial modnles basal on primary modules, subperichaetial innovations present, fertile only (Pyrrhobryum) (C) perichaetial modules formed distaUy on primary module, subperichaetial innovations present, fertile only (Cryphaea) (D) perichaetial modnles formed nonspecificaUy on primary module, subperichaetial innovations present, both fertile and vegetative (Amblystegium). 

In Rhizogonium and Pyrrhobryum Section Pyrrhobryum, innovations on the perichaetial modules form new perichaetial modules (Figure 14.5B), but not vegetative primary modules (discussed further in Chapter 3). The placement of these taxa in the pleurocarpous mosses, in a basal grade containing several acrocarpous taxa (BeU and Newton, 2005, see also Chapter 3), could indicate that the presence of subperichaetial innovations in these taxa is a retained plesiomorphic condition, whereas in taxa such as Amblystegium this condition is an independently derived reversal. 

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