Mosses are probably the bryophytes with which you are most familiar, but there are at least two other major lineages in the group liverworts and hornworts. Some bryologists are also arguing that Takakia and Sphagnum represent two other lineages. We shall not be discussing bryophytes in this course, but they are too intriguing to be completely overlooked. Tracheophytes The word Tracheophyte mans plants with tracheids. All tracheophytes have tracheids.
Tracheids are cells that are specialized for transporting solutions around a plant.
They also tend to have rather thick cell walls. With the acquisition of tracheids, and the evolution from them of cells are even more effective in solution transport and support, the stage was set for enormous diversification of photosynthetic land organisms. Tracheophytes have been far more successful than bryophytes, but they have not eliminated bryophytes. They are considered to represent a different lineage from bryophytes. The earliest vascular plant known is Cooksonia , which dates from 430 MBP, a mere 20-40 million years after the first algal land plant.