30 BULLETIN 824, U. S. DEPARTMENT OF AGRICULTURE, 
Frequently the analyst is called upon to make an estimation of the 
approximate quantity of insect flower stems that may be present in 
a powder. The fragments of stem tissue, occurring to some extent in 
every insect powder, are readily distinguished from the other tissues 
present. The stems, when ground, invariably break up into longi- 
tudinal sections. Cross sections seldom appear in the powder. 
These long strands of collenchyma cells, fibers, and vascular elements 
have a characteristic appearance, possessing brushlike or slightly 
frayed ends, differing very much from the shredded appearance of 
the fragments of bract tissue. For the purpose of estimating the 
percentage of stem tissues present in a powder, it has been found 
convenient to make up standard powders, containing known amounts 
of ground stem tissues, to be used for comparison with the commercial 
samples. Mounting the powder in xylol often facilitates the detec- 
tion of stem tissues. The patches of involucral tissue are invariably 
quite torn and coarsely shredded, and not in the long, smooth pieces 
characteristic of the stem tissue. The fruit (achene) tissue of the 
Dalmatian flowers occurs in squarish patches of short, thick-walled 
sclerenchyma cells, containing numerous crystals, many of them 
diamond-shaped. These crystals exhibit a variety of colors under 
polarized light, and are a means of distinguishing the Persian from 
the Dalmatian flowers, the Persian flowers lacking these crystals in 
the achene tissues. 
Microscopically some differences exist between the Persian and 
Dalmatian powders. As has already been mentioned, the marginal 
papilla? are somewhat different in the two species, although this 
character would not be recommended as a final means for distin- 
guishing between the two. The two varieties of flowers are much 
more easily distinguished from each other in the whole form than in 
the powder. 
Histology of Powder Elements. 
Powder, when pure, is a golden yellow, turning bright 3-ellow when 
mounted in potassium hydroxid (or other alkaline) solution. Japa- 
nese powders appear to be more yellow and aromatic than other com- 
mercial powders, and assume various greenish or ashen hues, depend- 
ing upon the amount of stems present. The pure powder possesses 
more or less of an aromatic odor. If stems are present in appreciable 
amount, the powder tends to have a characteristic sage or tealike 
odor. 
Phloroglucin and hydrochloric acid are useful in determining the 
amount of lignified tissue present. Lignified tissues assume a red 
coloration with these reagents. (Phloroglucin solution: 0.1 gram in 
10 cc of 95 per cent alcohol. Concentrated hydrochloric acid.) 
Potassium iodid solution of iodin turns starch a deep blue (0.05 gram 
