Missouri Botanical 
Garden Bulletin 
Vol. IV St. Louis, Mo., November, 1916 No. 11 
PLANTS IN ECONOMIC HOUSE 
(Continued from October Bulletin) 
GUMS 
_ Acacia arabica. Leguminosae. Gum arabic tree.—A 
moderate-sized tree found in India, Arabia, Egypt, and 
tropical and southern Africa. This, together with several 
other species of the genus, yields the gum arabic of com- 
merce, which is imported in the form of large, nearly black 
blocks or small rounded tears. It is used for imparting lustre 
to crape and silk, for thickening colors and mordants in 
calico printing, in the preparation of ink and blacking, as 
a mucilage, and in medicine. The wood of the tree is very 
durable if well seasoned, and is utilized in India for wheels, 
sugar and oil presses, rice pounders, agricultural implements, 
etc. The bark is used in dyeing and tanning industries. 
Castilloa elastica. Urticaceae. Panama rubber tree.—A 
large tree native of Central America. It furnishes the india- 
rubber of this region, and is known by the natives as the ule- 
tree. A large tree, when first cut, yields eight gs of 
milk, each gallon making two pounds of rubber. The plant 
has been introduced into India and Ceylon. 
_ Clusia Hilariana. Guttiferae. Balsam tree.—A gum resin 
is obtained from the different species of Clusia, a genus native 
of the West Indies and tropical America. The trees are 
small, much-branched, and soft-wooded. 
Clusia alba (balsam fig), India. 
Cryptostegia grandiflora. Asclepiadaceae. India-rubber 
vine.—A climber, native of India and South Africa. Its 
milky juice contains caoutchouc. The plant is common but 
the quantity of juice is not sufficient to make it of great com- 
mercial importance. 
Cryptostegia madagascariensis, Madagascar. 
Hevea brasiliensis. Euphorbiaceae. Caoutchouc.—A tree 
attaining 50-100 feet in height, with smooth trifoliate leaves 
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