The branch
primordia of the Leucodon and Pterogoniadelphus are studied and
their structure is found to be very similar to that of Brachytheciaceae and
Meteoriaceae. The first branch leaf points downwards, although the first
division of the branch initial cell cuts off the first merophyte in the “four
o’clock” position, i.e. in the same way as in other mosses. There is however a
difference from Brachytheciaceae as the first branch leaf is often split into a
number of lobes in some species, including the widespread Leucodon
sciuroides, obscuring the specific position of the first branch leaf. Possible
reasons of the similarities of this anomalous pattern are discussed.