Grass is a monocotyledonous plant whereas Hibiscus is a dicotyledonous plant. Presence of bulliform cells is a characteristic feature of monocot leaves. Bulliform cells are epidermal cells present in the epidermis of monocot leaves. When the bulliform cells in the leaves absorb water and become turgid, the leaf surface gets exposed. When they are flaccid due to water stress, they make the leaves curl inwards to minimise water loss. Thus, the leaves of grass fold due to the presence of bulliform cells.