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 PAPILLAE 



The papillae 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 papillae of the style differ in a 

 recognizable way from the papillae of the stigma. 



The papillae of the stigma of the ray and disk flowers of 

 arnica, anthemis, matricaria, and insect flowers differ greatly. 

 Even the papillae of the stigma of the ray and disk flowers differ. 

 In all cases observed the papillae of the ray flowers are smaller 

 than the papillae of the disk flowers. 



The papillae of the stigma of saffron (Plate 115, Fig. 3) are 

 long and tubular. These papillae are nearly uniform in diam- 

 eter, and the apex is blunt and rounded. The wall is slightly 

 granular in appearance. The papillae 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 

 papillae of that part of the style which emerges from the corolla 

 (Plate 116, Fig. i) are large and curved, and the walls are very 

 thick. The apex of the papilla is frequently solid. 



The papillae of the stigma of the ray flowers of anthemis 

 (Plate 117, Fig. i) have thin, slightly striated walls; while the 

 papillae of the stigma of the disk flowers (Plate 117, Fig. 2) are 

 longer, the walls are thicker, and the cell content is denser. 



The papillae of the stigma of the ray (Plate 117, Fig. 3) and 



