INSECT POWDER. 31 
of iodin and 0.2 gram of potassium iodid in 15 cc. of water). Chloral 
hydrate solution dissolves starch and clears the tissues (about 5 parts 
chloral hydrate in 5 parts of water). 
DALMATIAN FLOWERS. 
1. Numerous 3-pored, spiny pollen grains (PL III, figs. 3 and 4). 
2. Marginal papillae and papillae in surface view presenting a 
" puckered" or 3-cornered appearance (PL I, figs. 1 and 2). 
3. Sinuous, striated cells of epidermis of ligulate florets (PL II, 
figs. 1 and 2). 
4. Toothed fragments of the disc florets (PL III, fig. 2). 
5. Shredded fragments of involucral scales, strongly lignified (PL I, 
fig. 5). 
6. Attenuated and twisted horizontal cells of T-shaped hairs from 
the bracts (PL II, figs. 3 and 4). 
7. Occasional strands of stem tissue, much larger than other frag- 
ments, and usually possessing roughened or fibrous ends (PL I, fig. 6). 
8. Oil glands from the corolla and fruit. These are very seldom 
detected in the powder. 
9. Somewhat rectangular patches of sclerenchyma tissue from the 
fruit, containing numerous diamond-shaped crystals exhibiting a 
variety of colors under polarized light. Numerous isolated stone 
cells are also often found in powder ground from mature flower heads 
(PL I, figs. 3 and 4; PL III, fig. 6). 
PERSIAN FLOWERS. 
The diagnostic characters of the Caucasian or Persian flowers 
{Chrysanthemum roseum) in the powdered form are rather similar to 
those of the Dalmatian flowers. As already stated, the papillae of 
the ray florets differ somewhat, and the achene tissues do not contain 
the crystals characteristic of the Dalmatian flower fruit. The reddish- 
brown scarious margins of the bracts are often more striking in the 
Persian powder than in the Dalmatian. Collin (47), who also studied 
the Persian flowers, has summarized the principal diagnostic char- 
acters which distinguish them from the Dalmatian flowers. 
SUMMARY. 
Of course, the relative abundance of many of the tissues mentioned 
depends upon whether the powder is ground from open or closed 
flowers. Pollen is more abundant in closed-flower powder and 
sclerenchyma tissues in open-flower powder. The greater part of 
the pollen of closed or immature flower heads still remains in the 
closed "buds" or heads, the pollen not having as yet been scattered 
by the wind. On the other hand, the mature flower heads are practi- 
cally devoid of any great amount of pollen, but contain the mature 
