Answer:
Monocytes
Explanation:
Monocytes are the agranular white blood cells. These are the large cells with 10-24 micrometer diameter and are characteristic by the presence of kidney-shaped, round or lobed nuclei. The cytoplasm is blue-gray due to the presence of azurophilic granules. Cytoplasm gives a foamy appearance.
The azurophilic granules are very minute in size and are actually the lysosomes. Monocytes migrate from the blood into the tissues and differentiate into macrophages. Since the observed purple stained cells were large in size than RBCs (7-8 micrometer in diameter), have a kidney shaped nucleus, they are monocytes.