|This figure illustrates the maternal gametophyte calyptra |
and its location across the stages of sporophyte development.
An additional interpretation is presented by Haig. He views the waxy layers on the calyptra as slowing down or preventing the sporophyte from pulling up more water and potentially nutrients from the maternal plant.
Haig, D. (2012). Filial mistletoes: the functional morphology of moss sporophytes Annals of Botany, 111 (3), 337-345 DOI: 10.1093/aob/mcs295
These differing interpretations of the same phenomenon are not mutually exclusive. One is not right and the other is wrong. As Haig mentions, both maternal protection and restraint are likely to be occurring at the same time. This relationship between mothers and their offspring is a phenomenon that is seen across the plant and animal kingdoms.