24. BULLETIN 824, U. S. DEPARTMENT OF AGRICULTURE 
powder exhibited very little lienified tissue, but a large number of 
papillate fragments, the cuticle layer, and large epidermal cells, 
which were characterized by their striated surface. The powder 
from the receptacle showed small, yellowish-brown ceils which did 
not give the vanillin reaction. Thin-walled, porous cells were nu- 
merous, also lignified prosenchyma cells and large isolated vessels. 
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 inte iongi- 
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 quanti- 
ties of ground stem tissues, to be used for comparison with the com- 
~mercial samples. Mounting the powder in xylol often facilitates the 
detection of stem tissues. The patches of involucral tissue are in- 
variably 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 
papille 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. 
Histrotocy oF PowpER HLEMENTS 
Powder, when pure, is a golden yeilow, turning bright yellow when 
mounted in potassium hydroxid (or other alkaline) solution. Japa- 
nese powders appear to be more yellow and aromatic than other com- 
merciai 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 
quantity, the powder tends to have a characteristic sage or tealike 
odor. 
Phloreglucin 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 of iodin and 0.2 gram of potassium iodid in 15 ce. of water). 
Chloral hydrate solution dissolves starch and clears the tissues (about 
5 parts of chloral hydrate in 5 parts of water). 
0g ea 
