Question

The ____ phylum of seedless vascular plants has about 1000 known living species, including those in the genera Lycopodium and Selaginella; the gametophyte of some of these species cannot photosynthesize, and instead uses mycorrhizae to obtain nutrients.

Answer 1

The Pteridopyhta, phylum of seedless vascular plants has about 1000 known living species, including those in the genera Lycopodium and Selaginella; the gametophyte of some of these species cannot photosynthesize, and instead uses mycorrhizae to obtain nutrients.

Explanation:

The pteridophytes, most advanced group of plant among the cryptogams i.e. seedless plants.

They are first land plants that have developed a well defined vascular  system.

Ferns, horsetails etc are common members of this phylum.