It’s possible to identify Aloina ambigua in the hand by close examination of the mature capsule with a good x 20 hand-lens. Most of the time, plants are likely to be A. aloides, a far more common species. A close look at the mouth of the peristome of A. ambigua will show a narrow, pale band below the very long and elegant teeth. Under the microscope this is much clearer as a membrane of 3-5 rows of pale cells which is exposed above the peristome mouth, unlike A. aloides, where the teeth seem to rise directly from the mouth.
The capsules of Aloina are quite resilient and if they look near-mature but haven’t quite dropped their lids, it’s often possible to pull the lids off with sharp fingernails (or tweezers) to expose a perfectly developed peristome underneath.
Any confusion between Aloina ambigua and either A. rigida or A. brevirostris can also be eliminated if mature capsules are present. Ideally, pull a lid off so that the peristome is freshly exposed. In A. ambigua, the annulus – the ring of cells at the mouth of the capsule which helps the lid to drop – comprises small cells and remains in place once the lid has fallen. The two smaller/rarer species have an annulus of large, inflated cells which break off after lid dehiscence.Read the Field Guide account