Botany Photo of the Day

Thank you to Eric in SF@Flickr for sharing another photograph from Borneo (original | BPotD Flickr Group Pool). This photo is one of over 150 photographs in Eric's Borneo: All Other Plants, Flowers and Bugs photo set. Always appreciated, Eric.

What's particularly special about this moss is its freestanding height (and what that signifies). Eric noted a height approaching 15cm (6in) and alluded to online references suggesting a maximum height approaching 1m (3ft). That latter figure is higher than I've previously read for any member of this tallest family of mosses (~ 2/3 of that figure), but certainly plausible in ideal circumstances.

At the level of cells and tissues, Dawsonia is one of the most structurally complex of mosses. Some cells differentiate into analogues of the water and nutrient-conducting cells of vascular plants, while others become the thick-walled cells necessary to support the free-standing height. This combination, only present in a rudimentary way in some mosses (and absent in many), provides Dawsonia with the ability to internally transport water and nutrients. In most other mosses, the absence of this quality limits their height to under 10cm (4in).

Paradoxically, despite its tallest freestanding moss reputation, Dawsonia produces some of the smallest spores among mosses. Up to 65 million spores measuring 5-8 µm in diameter can be generated by a single sporangium, like the one shown in the upper part of this photo.

More photographs of Dawsonia longifolia (and there aren't many online) can be found in the University of Singapore's Interactive Malesian Moss Database.