-5- 
(b) The entire plant should be tested unless it is 
known that the active principles are localized in one 
part. 
(c) The plant should be tested shortly after it is 
collected, because many plant constituents, e_. £., the 
pyrethrins, deteriorate when the dried plant material 
is stored. 
(d) Several species of insects, representative of 
different orders, should be employed as test organisms. 
(e) The plant material should be tested as a con- 
tact poison, as a stomach poison, end as a fumi?ant by 
the aerosol method. 
(f) The plant material should be tested as a finely 
pulverized powder and in the form of extracts made with 
different classes of organic solvents.*** 
If these precautions are observed, many plants for- 
merly discarded as worthless may be found to have value. 
Botanists, chemists, entomologists, plant physiologists, and 
toxicologists should cooperate more than ever to find suitable insecti- 
cidal plants that can be introduced and grown in the countries in which 
insecticides are used on a large scale. 
As Mclndoo and Sievers ( 259 ) stated in 1924 the search for a 
plant which may be made commercially available as an insecticide at 
a reasonable price extends much further than merely finding a plant 
with satisfactory insecticidal properties. It involves, in addition, 
a study of the botanical characteristics of such a plant, its hab- 
itat, the available natural supply, the effective part of the plant, 
the means necessary for its collection and shipment, and, above all, 
the cost at which it can be delivered to the manufacturers in this 
country. 
COMMERCIAL AND EXPERIMENTAL CULTIVATION OF INSECTICIDAL PLANTS 
A book by Holman (198 ) on insecticides of vegetable origin w°s 
published in 1940. He named 9 countries as the principal producers 
of nicotine insecticides and 10 others ps lesser producers, pnd gave 
the total production as more than 3,593 long tons. He devoted 66 
pages to plants containing rotenone and allied compounds. Derris 
was grown commercially in 12 localities and was under experimental 
cultivation in 20 others. The derris root exported from ^British 
Malaya alone in 1939 amounted to 1,456 long tons, and 913 tons of 
