How to recognize Tortula porteri: This moss, formerly Desmatodon porteri, forms patches of tufted plants on stone. When moist the leaves on this little plant open and spread, when dry they are erect and somewhat contorted. These leaves are oblong-lanceolate to ovate-lanceolate with an acute tip and sometimes with a little hyaline apiculus. The midrib extends almost to the tip. The leaf cells are almost square and densely covered with papillae when viewed through a compound microscope. The leaf cells bordering the leaf margins are thicker walled than the interior and so the leaf has a yellowish border. There are separate male and female plants but it is still sometimes found with erect capsules on a 4.5-10 mm seta or stalk.
Where to find Tortula porteri: The plants of this moss are only 2-3 mm high so it is obvious on its substrate only as a green covering, or when it is dried out as a brown cover. Look for it on calcareous rock, which includes brick or concrete, and even sandstone if it is in a calcareous area.