Final answer:
Whisk ferns are native to subtropical and tropical regions, lack traditional leaves and roots, and are part of the class Psilotopsida. They perform photosynthesis in their green stems and have yellow sporangia.
Step-by-step explanation:
Whisk ferns are native to subtropical and tropical regions. These unique plants are characterized by their green branching stems that perform photosynthesis and lack traditional leaves, resembling a whisk broom. Whisk ferns are part of the class Psilotopsida within the phylum Monilophyta. They are unique for having yellow spherical sporangia and for their photosynthesis occurring in the stems. Despite their lack of leaves and roots, recent DNA analysis has shown that whisk ferns are closely related to true ferns and may have evolved through a reduction of these structures.