Figure 5.

Cryo-scanning electron micrographs of freeze-fractured moss sporophytes: Polytrichum juniperinum (a,b); Mnium hornum (c); Atrichum undulatum (d); Pogonatum aloides (e,f). (a,b) Unopened (a) and open (b) stoma subtended by a gas-filled intercellular space. (c) Sunken stoma subtended by a liquid-filled intercellular space. (d–f) In astomate taxa, intercellular spaces are also initially liquid-filled (asterisk, e) and the same process of liquid replacement by gas occurs in their fully expanded capsules (d,f). Scale bars: (f) 200 µm; (a–e) 20 µm.