I. | Gymnosperms lack vessels in their xylem. |
II. | In stems the arrangement of primary xylem is called an exarch. |
III. | Angiosperms lack sieve tubes and companion cells. |
IV. | Phloem fibres are generally absent in primary phloem. |
1. | Guard cells invariably possess chloroplasts and mitochondria |
2. | Guard cells are always surrounded by subsidiary cells |
3. | Stomata are involved in gaseous exchange |
4. | Inner walls of guard cells are thick |