278 HISTOLOGY OF MEDICINAL PLANTS 
disk flowers (Plate 117, Fig. 5) of matricaria are similar in 
structure, but the papillz of the disk flowers are larger. 
The papille 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 
papilla of the disk flowers (Plate 115, Fig. 2) are long and 
tubular, and the walls are thick. 
The papillz of the stigma of the ray flowers of arnica (Plate 
115, Fig. 1) are very short and tubular. The walls are thin 
and the cell contents appear as small, bright-yellow globules, 
while the papilla 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. 1). 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- — 
