Fig. 3.6-1. Section of bean cotyledon. These are storage parenchyma cells in a germinating bean seed, storing both starch grains (stained pink) and protein (colorless round or angular particles). The very dark red bodies are nucleoli, and in several cells, the nuclei are visible as a gray mass surrounding the nucleoli. These storage cells remain alive after they have filled themselves, and they will be active in unloading the stored carbohydrates and proteins as the seed germinates. In many monocots like corn, wheat and rice, the storage parenchyma cells die after they have filled themselves, and all unloading is carried out by enzymes secreted by other cells. Many of the walls are indistinct in this section, having taken up only a little of the stain, but where the walls are distinguishable, they are thin.