Mosses are among the most desiccation-tolerant of all plants. They can be completely dried at the cellular level and recover completely. When re-wet after months or years of being dry, they begin photosynthesis within 5 minutes! For more information about desiccation-tolerance.

The mosses are also interesting phylogenetically. Mosses are a single, diverse lineage of some 15,000 species; the moss lineage as a whole is the closest living relative of the "vascular plants" (i.e., the diverse lineage containing ferns, horsetails, pines, flowering plants, etc.). These two big lineages of land plants, that last shared a common ancestor some 500 million years ago, have adopted two contrasting life styles. The leafy green part of the moss plant is the haploid generation (i.e., with each cell containing one set of chromosomes, as human sex cells do). By contrast, the green leafy plant of all vascular plants is the diploid generation (i.e., with each cell containing two sets of chromosomes, as in all cells of the human body). The mosses remained small in stature, occupied microhabitats and retained their desiccation-tolerant water relationships, while the vascular plants became large, structurally complex, and ecologically dominant ... two different strategies for being a land plant. For more information about green plant evolution, see the "Deep Green" website.

The leaves of Tortula princeps are only one cell thick, and each one has a long, clear hairpoint, and two kinds of leaf cells: large, clear, window-like ones below, and small, green, bumpy ones above. There is a tremendous difference in the wet and dry appearance of this moss; when wet it is green, with each leaf recurved giving the plant an appearance of a "star" when viewed from above; when dry it is red-brown and the leaves are folded and twisted together around the stem.

This web monitoring project takes advantage of this morphological shift -- our goal is to determine the actual water budget of this plant in real time. No one knows how many hours during a year (or with what periodicity) a desiccation-tolerant moss is wet (and thus active). Thus in addition to providing an exciting and entertaining website where you can watch moss photosynthesize and grow in real time (!), this project has a serious scientific side: we are automatically recording data about changes in the water and light status of this clump over several years.

The leaves of Tortula princeps are only one cell thick, and each one has a long, clear hairpoint, and two kinds of leaf cells: large, clear, window-like ones below, and small, green, bumpy ones above. There is a tremendous difference in the wet and dry appearance of this moss; when wet it is green, with each leaf recurved giving the plant an appearance of a "star" when viewed from above; when dry it is red-brown and the leaves are folded and twisted together around the stem.

The long cylinders on stalks are the capsules; the diploid part of the life cycle where spores are produced. Look for the peristome, which is the long twisted set of teeth at the end of the capsule (see how the free, twisted ends of the teeth arise from a basal membrane that looks like delicate basket-work); it is this twisted structure that gives the genus Tortula its name.