Perichaetial module

Vouchers for scoring of characters for taxa in grade R and in the hypnodendroid pleurocarp clade are provided in Table 3.1. Taxa in the Hypnidae were assumed to be pleurocarpous with distally produced perichaetial modules and to lack subperichaetial innovations, and taxa outside of the clade that includes grade R and the higher pleurocarps were assumed not to be pleurocarpous. Perichaetial module position and presence/absence of subperichaetial innovations were considered applicable to pleurocarpous taxa only (see discussion). 

The possibility that reduced perichaetial modules could be at the primary level of the branching hierarchy was considered, but in none of the plants examined was there convincing evidence of this. Similarly, all innovations produced on perichaetial modules appeared to develop into other perichaetial modules rather than vegetative primary modules (i.e., the sequence of module types is hierarchical and unidirectional). Individual primary modules often produce both perichaetial mod-... 

T Vegetative primary module (determinate) Pleurocarpous perichaetial module... 

FIGURE 3.4 Optimization of presence/absence of subperichaetial innovations on pleurocarpous perichaetial modules onto tree C. (A) Under accelerated transformation (ACCTRAN). Continued. 

FIGURE 3.6 Optimization of perichaetial module position onto tree C under delayed transformation (DELTRAN). (A) Distally produced peiichaetial modules assumed to be plesiomorphic. Continued. 

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. 

The morphological character pleurocarpy is viewed here in the strict sense, as the formation of archegonia on a reduced lateral module that has juvenile perichaetial leaves but lacks differentiated... 

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