Assertion: moss's structure | /r/CapableOf | call protonema
Facets:
Source sentences:
text: The spores begin their development, forming a mat-like structure called a protonema.
text: Moss spores germinate to form an algae-like filamentous structure called the protonema.
text: They germinate into a filamentous structure called a protonema, from which buds develop.