describe atleast two bryophyte characteristics that limit their size?

Limited by Scale ?Being Without Lignin
Being without lignin imposes other limits on plants. It means they have no tracheids or vessels, hence
lack the type of conducting system known inmore traditionally, those known as vascular plants. This implies that they lack true leaves, hence making it more appropriate to call their photosynthetic extensions phyllids (but few bryologists do, choosing to call them leaves). The bryophytes are more appropriately termed non-tracheophytes (rather than nonvascular plants

Limited by Scale ? Needing to Swim
One might suggest that getting a sperm to an egg
without windborne pollen necessarily limits the size of a
gametophyte on land. This suggestion certainly could be
supported by the total absence of large terrestrial
gametophytes in any plant group. Since the sperm must
find a film of water in which to swim, and cannot swim
very far, it must rely on short stature and various splashing
mechanisms in order to reach the female reproductive
structures, especially when they occur on another plant.
Such a limit is supported by the small size of all
gametophytes in the plant kingdom.