A very important feature of ferns is shown in Figure 21-29: Their shoot xylem is not solid as it was in the rhyniophytes. In the evolution of ferns and seed plants, there was the evolution of pith. A stele with a pith is called a _________________. Another significant feature of ferns is that the phloem occurs both to the outer side as well as the inner side of the xylem. Where does it occur in the vascular bundles of flowering plants?

Figure 21-29

Transcribed Image Text:

Cortex- 6 Xylem- Phloem Pith (A) Xylem Leaf gap (B) Leaf trace (D) Xylem -Phloem -Xylem Phloem Phloem