274 HISTOLOGY OF MEDICINAL PLANTS 
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 PAPILLA 
The papillz of the stigma of most flowers form a character- 
istic element even when the flower is powdered. In the case 
of composite flowers the papillae of the disk and ray flowers 
differ. In American saffron the papille of the style differ in a 
recognizable way from the papille of the stigma. 
The papille of the stigma of the ray and disk flowers of 
arnica, anthemis, matricaria, and insect flowers differ greatly. 
Even the papilla of the stigma of the ray and disk flowers differ. 
In all cases observed the papilla of the ray flowers are smaller 
than the papillz of the disk flowers. 
The papillz of the stigma of saffron (Plate 115, Fig. 3) are 
long and tubular. These papillze are nearly uniform in diam- 
eter, and the apex is blunt and rounded. The wall is slightly 
granular in appearance. The papiilz of the stigma of American 
saffron (Plate 116, Fig. 2) are short and tubular. Each papilla 
is broadest at the base and tapers to a slender point. The 
papilla of that part of the style which emerges from the corolla 
(Plate 116, Fig. 1) are large and curved, and the walls are very 
thick. The apex of the papilla is frequently solid. 
The papilla of the stigma of the ray flowers of anthemis 
(Plate 117, Fig. 1) have thin, slightly striated walls; while the 
papilla of the stigma of the disk flowers (Plate 117, Fig. 2) are 
longer, the walls are thicker, and the cell content is denser. 
The papillz of the stigma of the ray (Plate 117, Fig. 3) and 
