Q.Why pollen grains can remain well preserved as fossil?

The androecium, the male reproductive whorl of a flower, is made up of individual stamens, each consisting of a filament, a connecting tissue (the connective), and an anther bearing two lobes (thecae). A typical anther is dithecous (two-lobed) and tetrasporangiate (four pollen sacs in total, two per lobe). In its immature state the anther is a solid mass of parenchyma covered by a single epidermal layer; some hypodermal cells then differentiate into archesporial cells, each of which divides into an inner sporogenous cell (which builds up the pollen-producing sporogenous tissue) and an outer primary parietal cell (which builds the anther wall). The mature anther wall has four distinct layers: the outer, protective epidermis; the endothecium, whose radially elongated, fibrously thickened cells help the anther split open at maturity; one or two thin, often disintegrating middle layers; and the innermost tapetum, the nutritive layer that directly nourishes the developing pollen mother cells throughout microsporogenesis. …