Perichaetia

Paraphyses in perichaetia present state 1 present or absent (either in perichaetia prior to sporogone development or in full grown ones) state 2 absent state 3. 

Leaf-like paraphyses in full grown perichaetia absent state 1 occasionally present state 2. 

Stalk of full grown perichaetia at least occasionally set with rhizoids state 1 glabrous state 2. 

In this overview we include structures that are inserted directly on the stem, and structures that are mostly found on the stem, but which may in some cases be found also on the leaves. The main topic of this chapter is not perichaetia and perigonia, but these highly specialized organs are nevertheless discussed briefly under Branches. ... 

Subterminal branches are sympodial branches that develop just below a terminal gynoecium or androecium. Subterminal branching is especially common in acrocarpous mosses, and in many groups most of the shoots are just a series of subterminal branches (e.g., Pottiaceae, Grimmiaceae). Subterminal branches, or secondary axes from the basal part of perichaetia in cladocarpous mosses, are present in many members of the Hypnales (La Farge-England, 1996), but their role in the plant architecture is almost never comparable with that of ordinary branches. 

Camptochaete arbuscula (Figure 15.3A) has an architectural unit made up of a primary module, consisting of a stolon, stipe and frond axis secondary modules, determinate lateral branches of the frond axis, the frond axis and the lateral branches together making up the frond tertiary modules, determinate lateral branches of the secondary modules perigonia and perichaetia (lateral on secondary fertile axes on the frond axis) and flagelliferous frond axis tips which become... 

Reiteration is typically sympodial, and also may be monopodial. Reiteration may be full or partial. Full reiteration reproduces the basic repeated units of constrnction of mosses, inclnding all the axis types produced by any particular species, as well as any other structures (perigonia, perichaetia, etc.). In mosses this means reproduction of the primary modnle. The plants are made np of a series of connected primary modules and all the structures that are borne on them. Reiteration may be sympodial or monopodial. 

PLATE 16.3 Palaeodichelyma sinitzae Ignatov Shcherbakov, from Daya (all from 5092/la, holotype, except (B), which is counterpart, 5092/lb). (A) Leafy shoot with putative perichaetia (B) stem fragment with leaf base and putative perichaetium (C) perichaetia (D) part of leafy shoot (E) leaf base (F) stem surface (G) cells of leaf base. 

In conclusion, the question, Did pleurocarpous mosses originate before the Cretaceous has to be answered, Yes, they did. Overall similarity and, especially lateral perichaetia of Palaeodichelyma provide enough evidence for this. Even if the dating of the deposits with Palaeodichelyma shifts to the basal Cretaceous, the fact of its distribution in several localities means its origin must be at least in the Late Jurassic. Bryokhutuliinia and Muscites fontinaloides can also be pleurocarps, though additional evidence is necessary to say this for sure. 

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