How to recognize Callicladium haldanianum: This moss grows hugging fallen tree trunks and forms thin mats on them. The capsules are long and straight below but curved just below the peristome. The plants sometimes look somewhat flattened or complanate. The leaves have a short double costa and under the microscope the ovate lanceolate leaves have several rows of enlarged clear alar cells at the corners of the base of the leaf. Under the microscope, if you examine a stem with most of the leaves stripped off, you can find pseudoparaphyllia around the bases of the bumps on the side of the stem that are the beginning of new branches. These pseudoparaphyllia look like thin little leaves, that are often only a few cells wide; some look like single celled filaments, but you can always find some several cells wide.
Where to find Callicladium haldanianum: Look for this moss on rotten logs and in wet areas on soil and rocks.