2 BULLETIN 1201, U. S. DEPARTMENT OF AGRICULTURE. 
rated; (2) characteristics of growth, whether annual or perennial. 
large or small, abundant or sparse; (3) portion of the plant effective ; 
and (4) nature of the active constituent and the means necessary to 
make it available for use. 
The most desirable type of plant is no doubt one which grows 
abundantly in a wild state, preferably in areas not readily adapted 
to the cultivation of valuable crops. Under such conditions the 
material could be obtained with the minimum of expense, the only 
cost Icing that of collection and preparation. Less abundant growth 
involves greater cost in collecting, and in case the plant must be 
cultivated it must bring sufficient return to compete with other 
crops adapted to that particular region. Perennials are much more 
desirable than annuals, since their products can usually be collected 
from year to year. Leaves and branches of trees or shrubs or the 
entire herbaceous portions of hardy perennials can be most economi- 
cally obtained. On the other hand, the collecting of fruits or seeds 
or the digging of roots or rhizomes can, as a rule, be much less 
economically done. In the case of small plants, gathering the 
roots usually means the destruction of the plant, which, in time, is 
likely to reduce the supply unless the plant is under cultivation. 
The character of the active constituent has an important bearing 
on the handling necessary in its preparation for the market. Sub- 
stances like alkaloids and toxic resins are usually not subject to ready 
decomposition, and material containing such constituents need not 
be dried and handled with more than ordinary care. On the other 
hand, plant material depending for its action on glucosides must be 
carefully dried in order to inhibit decomposition of such constituents. 
In the case of plants native to foreign countries, especially the 
Tropics, this is an important matter, since the collecting is usually 
done by natives, and control of conditions of handling is likely to 
be difficult. Long voyages, especially by sea, are furthermore likely 
to cause deteriorating changes in such plant materials. 
It is evident, therefore, that the search for a plant which may be 
made commercially available as an insecticide at a reasonable price 
extends much farther than merely finding a plant which possesses 
insecticidal properties to a satisfactory degree. It involves, in addi- 
tion, a study of the botanical characteristics of such a plant, its 
habitat, the available natural supply, the means necessary for its 
proper collection and shipment, and, above all, the cost at which 
it can be delivered to the manufacturers in this country. 
METHODS USED BY THE WRITERS IN PREPARING PLANTS 
FOR INSECTICIDES. 
To determine the insecticidal properties of plant material, a num- 
ber of different ways of preparing it are necessary. This is espe- 
cially true if the material is of unknown composition. Tests on in- 
sects may be made by applying the material (1) in a dry, finely 
ground condition as a dusting powder; (2) in the form of water ex- 
tracts made with hot or cold water; or (3) as extracts made with 
other solvents, such as benzene, gasoline, petroleum ether, and alco- 
hol. In all cases the material must be thoroughly dry, and then be 
reduced to a powder. If the powdered material is to be used as such 
