Fig. 9.3-9. Transverse section of stamen in lemon flower (Citrus limon). This is a transverse section of the anther, the part of the stamen that actually produces the pollen grains. As part of pollen development, the cells lining the anther lumen – a layer known as the endothecium – secretes materials that are essential for the proper maturation of the pollen grains. In many cases, secretory processes in plants involve interaction with animals (deterring herbivores or attracting pollinators), but in processes like this in the anther, the secretion is a mechanism by which one part of a plant affects another part of the same plant.