In santonica the pollen grains have smooth, unequally thickened walls, which are strongly constricted at three points, the outline resembling three half-circles placed together. In elder flowers the pollen grains appear circular or three-parted. The wall is of nearly uniform thickness, even at the constricted part of the grain. In century minor the pollen grains show three pronounced restrictions. The wall at these points is very thin. In pichi flowers the pollen grains are either circular or three-sided and three-pointed. Inside of each point there is a nearly white pore. In some of the grains the pollen tube has grown out of one of the pores. In cyani flowers the pollen grains are longer than broad and the cell contents appear to be divided into two end portions and an elevated middle portion. SPINY-WALLED POLLEN GRAINS In anthemis the pollen grains have unequally thickened walls constricted in three places. The spines are short, broad at the base, and sharp-pointed. In arnica flowers the pollen grains show three light-colored pores and numerous short spines. In calendula flowers the pollen grains show one or more pores, typically three pores. These pores appear as white spots, and the wall immediately over the pore is smooth and thinner than the remaining part of the wall; the spines are very numerous. In cassia flower pollen grains the outer wall is extended into a number of rounded projections which are frequently arranged in sets of fours. In American saffron flowers the pollen grains show one, two, or three light-colored pores; the spines are short and broad. In blue malva flowers the pollen grains are spherical and the outer wall extends into numerous spinelike projections. It will be observed that the spiny-walled pollen grains differ greatly in size, the smallest being the pollen grain of anthemis and the largest being the pollen grain of blue malva flowers. In matricaria are numerous, greenish-brown, spiny-walled pollen grains. In anthemis are multicellular, uniseriate non-glandular hairs with three or four short, broad, yellow-walled basal cells and a greatly elongated, thin, gray-walled apical cell. In arnica are multiseriated branched hairs of the pappus, and numerous large, yellowish, spiny-walled pollen grains. STIGMA PAPILLÆ The =papillæ of the stigma= of most flowers form a characteristic element even when the flower is powdered. In the case of composite flowers the papillæ of the disk and ray flowers differ. In American saffron the papillæ of the style differ in a recognizable way from the papillæ of the stigma. The papillæ of the stigma of the ray and disk flowers of arnica, anthemis, matricaria, and insect flowers differ greatly. Even the papillæ of the stigma of the ray and disk flowers differ. In all cases observed the papillæ of the ray flowers are smaller than the papillæ of the disk flowers.