Figure 2.

The pseudostomata of Sphagnum are anatomically and functionally unique amongst land plants. (A) Pseudostomata are found on the sporophyte capsule and are covered in a calyptra that ruptures once the sporophyte has reached maturity (scale bar = 300 μm), (B) pseudostomata are not subtended by intercellular air spaces (scale bar = 75 μm). (C) Turgid pseudostomata can be found on a mature sporophyte under the calyptra. (D) As the sporophyte begins to dehisce the guard cells begin to lose turgor. (E) By the time the calyptra has ruptured and the capsule has dehisced the guard cells have shrunken apart at the top, appearing open (scale bars = 60 μm). The stomata of mosses outside the Sphagnopsida, like Funaria hygrometrica Hedw. (F), also open and become locked in that state due to a completely inflexible, thickened wall surrounding the pore (G) which renders them immobile (scale bars = 10 μm).