effect of the calyptra on the plane of guard cell mother cell division in Funaria and Physcomitrium capsules

The calyptra influences the plane of division in guard cell mother cells of Funaria and Physcomitrium. Normally, capsules expand while sheathed by the calyptra and the axes of the stomata are parallel to the axis of the capsule in both genera. Removal of the calyptra from an elongating sporophyte leads to seta thickening prior to capsule expansion and an essentially random orientation of stomata. If the calyptra is removed from a sporophyte of Funaria at the time the division of the guard cell mother cells is expected, guard cells of abnormal shape and undivided guard cell mother cells are found in unusually high frequency.