1. Found in gymnosperms and pteridophytes.
2. Not associated with companion cells.
3. Sieve areas without sieve plates.
4. Long, elongated cells with tapering end walls.
1. Found in angiosperms.
2. Associated with companion cells.
3. Sieve areas with sieve plates.
4. Shorter but wider cells placed one above the other and connected at the end walls by sieve pores.