INSECT POWDER 23 
Kirkby (156) and Verneau (285) have called attention to one dis- 
tinction which they believed might aid in identifying the Persian 
powder. They found the papille of the ray florets to be larger than 
those of the Dalmatian florets, thickened somewhat more at the apex, 
and with sides making a wider angle. Malfatti (486) has gone into 
the description of the Caucasian (Chrysanthemum rosewm) flowers 
quite extensively, figuring the various parts of the flower head. 
Siedler (258) describes the physical characteristics of powders made 
from different parts of the omer: 
MicroscoPpicAL EXAMINATION oF Insect PowpzER 
Before attempting the critical examination of a commercial insect 
powder, the microscopist should become thoroughly familiar with 
the various parts of the insect flower head, in the whole as well as 
in the powdered condition. It has been found advantageous to sep- 
arate the disk and ray florets, the achenes and bracts, grinding them 
separately to the average fineness of a commercial powder. A study 
of these powders ground from the separate parts of the flower head 
will Enable one to readily recognize them in a commercial sample. 
Powders ground from closed and open flowers should also be ex- 
amined. The closed-flower powder is rich in the spiny, 3-pored 
pollen grains, and should not contain an excessive amount of scler- 
enchymatous tissue. The presence of considerable sclerenchyma- 
tized tissue usually indicates very mature (open) flower heads. The 
powder of open flowers does not contain as much pollen, but tissues 
EN achene are present in appreciable quantity (PI. IV, figs. 
1 and 2). 
The powder to be analyzed microscopically should be thoroughly 
mixed. This is best done by spreading the sample upon a sheet of 
white paper and mixing the powder with a spatula. Flattening 
the powder out upon the paper often reveals the presence of whole 
unground pieces of material which can be transferred to a micro- 
scope slide and examined. After mixing, a composite sample is 
taken from various parts of the sample. A small quantity of the 
powder is placed upon a microscope slide, a drop or two of distilled 
water added, and the cover glass adjusted. If examination of the 
water mount reveals the presence of any foreign starch, a small 
quantity of a solution of iodin in potassium iodid is drawn under the 
cover glass. This reagent stains blue any starchy material that may 
be present. For further examination a small portion of the powder 
should be mounted in chloral hydrate solution and gently heated over 
the flame. This solution serves to dissolve any starch that may be 
pees and clears the tissues generally. Until the microscopist has 
ecome thoroughly familiar with the Pyrethrum tissues, standard 
samples ground from the various parts of the flower head should 
be kept on hand for comparative study. 
Siedler (258) aaploved phloroglucin and hydrochloric acid in de- 
tecting the presence of lignified tissues (vanillin reaction). On ap- 
plying these reagents to disk-flower powder very little lignified tissue 
was evident, although pollen grains and fragments of papillate cells 
were numerous. The powder from the involucre showed a large 
number of woody elements, isolated vessels, thick-walled prosen- 
chyma cells, scleroids, and pitted parenchyma cells. The short- 
stalked T-hairs were characteristic of this powder. The ray-flower 
