Large, empty colourless cells of the adaxial epidermis along the veins of grass leaves are:

Step-by-step solution

In monocots like grass, the upper epidermis or adaxial surface has a motor or bulliform cells. These cells are large, empty colourless cells and are present along the veins. These cells by osmotic changes help in the rolling and unrolling of leaf lamina, which regulates the rate of transpiration.