Question

why potato and ginger are called modified stems?

Answer 1

because they have bulbils in potato and in ginger their is node and internode

Answer 2

Answer:

Potato is a stem and sweet potato is a root because, The stem of the potato has undergone modifications in order to store food which is termed as stolons. Potato tubers (modified stems are usually called 'tubers') have buds that sprout stems and leaves from them while roots do not possess these properties.