In classifications that consider the possession of vascular tissue of equivalent significance to the seed-bearing habit, a division containing all the nonseed-bearing * vascular plants (compare Tracheophyta ). Its members show a heteromorphic alternation of generations and the gametophyte is often nutritionally independent of the sporophyte. The sporophyte differs from that of seed-bearing plants (see Spermatophyta ) in lacking vessels in the xylem. Some species exhibit homospory in contrast to spermatophytes, which are always heterosporous. The Pteridophyta contains the subdivisions or classes * Psilopsida , * Lycopsida , * Sphenopsida , and * Pteropsida. |
