In classifications that consider the possession of vascular tissue of greater significance than the seed-bearing habit, a division containing all the * vascular plants. It is divided into the subdivisions * Psilopsida , * Lycopsida , * Sphenopsida , and * Pteropsida. The psilopsids are considered the most primitive as they lack true roots and a well defined phloem. These features are properly developed in the other subdivisions. Also the psilopsid gametophyte resembles the sporophyte in being dichoto-mously branched and possessing vascular tissue, while in the other subdivisions the gametophyte is comparatively reduced. |
