166 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 
the principal supply now comes. Prices vary at present from 60 cents to $1.20 
per pound, depending upon quality. The competition of an artificial coal-tar 
product called alizarin, which threatened at one time to entirely replace indigo, 
is not feared so much as formerly, it having been found that indigo dyes are 
preferable for many purposes. 
This crop was cultivated on a considerable scale in our Southern States during 
the eighteenth century, about 1,500,000 pounds being exported in 1794. The 
conditions were, however, not sufficiently favorable to enable the planters to 
withstand the competition of tropical countries where three crops can be cut each 
year, and production gradually ceased. At present we import indigo to the value 
of about $1,600,000 annually. Cultivation and manufacture are simple processes 
and have been well summed up in the following paragraph, extracted from a 
circular letter compiled by Mr. Lyster H. Dewey, of the Division of Botany. 
Although these operations are not complicated, much skill and experience are 
necessary in order to decide how long to continue the various stages of fermen- 
tation and aeration: 
‘Indigo is cultivated on sandy soil. The seeds are sown in spring either in 
drills or hills or broadcast. When sown in hills or drills it is cultivated or hoed. 
It is ready to cut from 45 to 60 days after seeding. The indigo is extracted by 
placing the plants, either fresh or after they have dried like hay, in a large tank, 
where they are covered with water. They are allowed to remain in the water 
about twenty-four hours, or a shorter time if the water is heated. It should not 
be boiled. The water is then drawn off into another tank, where it is stirred for 
at least three or four hours. Sometimes limewater is added during the stirring 
process to aid in precipitating the indigo. This is either allowed to settle in the 
tank where it is stirred or, more frequently, drained off into a third tank. The 
settling requires about twenty-four hours. When the indigo has settled to the 
bottom, leaving the water above practically clear, the water is carefully drawn off 
and the indigo is taken out and dried on cloths. When it is dried to about the 
consistency of molding clay it is usually made up into balls, and these are dried 
in the shade. When thoroughly dried and hard they are packed for market. The 
yield of indigo varies from 50 to 140 pounds per acre for each cutting. The aver- 
age yield in Venezuela is about 112 pounds, but in the United States it was 
considerably less.”’ 
When planted in rows, these are about 2 feet (60 centimeters) apart,and 15 pounds 
(7 kilograms) of seed wre used per acre. Blossoming is sometimes delayed for 
twelve weeks, and in some countries exposure of the cut indigo to the sun is con- 
sidered detrimental. The average yield has been given as 300 pounds (1-12 kilo- 
grains) per acre. Although belonging to the Leguminosae, the indigo plant is 
said to rapidly exhaust the soil, so that planting on the same land can not be indefi- 
nitely repeated. Alternation with the pigeon-pea (Cajanus) has been advised. 
In different countries there are also considerable differences in the methods of 
extraction, and in some parts of India the precipitate is boiled before being finally 
pressed and dried. This method is now defended by the best authorities as an 
improvement over that formerly followed in the United States and still generally 
prevalent in the American tropics. 
The important difference in the market prices quoted above shows that quality 
is important in this product as in every other, and while indigo can not, perhaps, 
be recommended to the general farmer in Porto Rico, it is by no means certain 
that a properly organized plantation with a well-equipped and intelligently 
directed factory would not be a profitable enterprise. The production of indigo 
of high quality on a small scale is seldom accomplished, because of the absence 
of the most favorable conditions and best appliances; but in a large enterprise 
these can be profitably provided. 
