Exostome

Endostome processes, when present, alternating with the teeth of the exostome. 

Endostome processes opposite the teeth of the exostome, either free or united with them, but the peristome sometimes entirely wanting hypophysis sometimes highly developed acrocarpous mosses.Order Splachnales (Funariales)... 

Exostome teeth present state 1 absent state 2. 

Exostome teeth 70 pm wide at least state 1 70 pm wide at most state 2. 

Exostome teeth partly or entirely bordered above the base state 1 not bordered or slightly bordered state 2. 

Ornamentation of the dorsal plates in the basal third of the exostome teeth conspicuously striate (striae set with papillae or not) state 1 smooth, papillose, or weakly striate near the tooth base state 2. 

Papillae on the dorsal plates of the exostome strictly low state 1 (occasionally) high state 2. 

Trabeculae in the middle parts of the exostome teeth shot to strongly protruding and closely set state 1 very short to short and distant state 2. 

In Catharomnion ciliatum, the peristome is endostomial only. Therefore, the states of exostome characters 43 9 are coded as unknown for this species. 

Exostome colour Mostly red, red-brown, or orange-brown Pale whitish yellow Yellow-brown or brownish yellow... 

Exostome furrow No furrow No furrow No furrow Furrowed cm split, rarely unfiirrowed... 

Exostome border at zone of transition in OPL pattern Not widened Not widened Widened or (sometimes in Thuidiaceae) not Not widened... 

Primary peristomial layer of exostome Normal Normal Normal Mostly strongly devel( )ed... 

Besides frequently having orthotropous capsules, epiphytic pleurocarps possess several other sporophytic character states more often than species of other habitats. These include short setae, ovoid to cylindrical and straight capsules, round stomatal pores, lack of or a poorly developed separating annulus, rostrate lids, papillose lower exostome outer surface, reduced exostome primary... 

Previous studies on variation in peristome morphology include an intergeneric snrvey of endostome variation in 70 species of diplolepidous mosses (Shaw and Rohrer, 1984), and stndies of Bryaceae (Shaw, 1985) and Brachytheciaceae (Ignatov et al., 1998). The infraspecific variation in the exostome ornamentation in the reduced peristome of Pterigynandrum flliforme had resulted in a number of varieties being described (Buck, 1980). 

FIGURE 12.1 Diagram of a transverse section through the developing capsule of Entodon in the region of the peristome showing the relationship of the OPL, PPL and IPL to the exostome and endostome. 

The exostome is formed from the common periclinal cell wall pair between the inner wall of the OPL and the outer wall of the PPL. The endostome is formed from the common periclinal cell wall pair between the inner wall of the PPL and the outer wall of the IPL (Figure 12.1). Autolysis of the anticlinal walls of the cells between the exostome and the endostome separates the two rings of the diplolepidous peristome, while autolysis of the periclinal walls between adjacent teeth separates the structures within each ring of the peristome. In reduced peristomes this autolysis may be incomplete, leaving adjacent structures partially attached. 

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