Plants without well-differentiated stem, root and leaf are kept in ____________.

Division Thallophyta:

1. They are green and do not have well-differentiated roots, stems, and leaves.
2. Such a type of body design is called a thallus.
3. The plants in this group are commonly not called algae.
4. These plants are predominantly aquatic.
5. Some of them also grow attached to rocks, on the bark of trees, and on the surface of moist soil.
6. They are unicellular (Chlamydomonas) or multicellular.

Final answer: Plants without well-differentiated stem, root and leaf are kept in thallophyta.