278 HISTOLOGY OF MEDICINAL PLANTS 



disk flowers (Plate 117, Fig. 5) of matricaria are similar in 

 structure, but the papillae of the disk flowers are larger. 



The papillae of the stigma of the ligulate flowers of insect 

 flowers (Plate 117, Fig. 5) are tubular; the walls are striated, 

 and in each papilla there is a small yellow globule, while the 

 papillae of the disk flowers (Plate 115, Fig. 2) are long and 

 tubular, and the walls are thick. 



The papillae of the stigma of the ray flowers of arnica (Plate 

 115, Fig. i) are very short and tubular. The walls are thin 

 and the cell contents appear as small, bright-yellow globules, 

 while the papillae of the stigma of the disk flowers (Plate 116, 

 Fig. 3) are broadest at the base, the apex is pointed, and the 

 yellow globules are larger. 



The solitary hairs are divided into the branched and non- 

 branched hairs. 



POWDERED INSECT FLOWERS 



The microscopic examination of insect powder is difficult for 

 the reason that there are so many elements to be constantly 

 kept in mind. The parts of the flower which contribute char- 

 acteristic cells are the stem, involucre, ray flowers, disk flowers, 

 and the receptacle. In each of these parts there are many 

 different types of cells. 



There are practically two types of flowers found in insect 

 powder of commerce: first, closed or immature flowers, and 

 secondly, open or mature flowers. As explained above, the 

 half-open flowers consist largely of the two above-named varie- 

 ties. Let us first consider the structure of the closed insect 

 flowers as illustrated in Plate 118. 



The involucre has many characteristic cells. The more 

 prominent ones seen in the powder are the edge of the scale with 

 the attached hair (Fig. i). These hairs (Fig. 3) are T-shaped. 

 The terminal cell is expanded laterally, and it terminates in 

 two points. Connecting the terminal cell with the epidermis 

 are two or three cells which are slightly longer than broad. 

 In the powder the terminal cell is usually attached to fragments 

 only of the supporting cells. Fibres of the bracts have thick, 

 wavy, porous walls, and they have a tendency to occur in masses. 

 The upper epidermis (Fig. 4) of the ray-flower petal is promi- 



