latexes of other species and preventing their coagulation 
(Schultes in Bot. Mus. Leafl. Harvard Univ. 12 (1945) 
11; Seibert in Ann. Mo. Bot. Gard. 34 (1947) 269), it 
is probable that the natives gave up the exploitation of 
their caatinga trees upon discovery of this characteristic 
of HZ. nitida. 
Material for chemical study was taken from bark and 
leaves of the tree which supplied the herbarium collection 
Schultes & Lopez 9586. The analyses of this material are 
as follows: Bark—‘‘ Resin (acetone extract) 2.57 9% ; Rub- 
ber hydrocarbon (benzene extract) 0.64%. Poor, soft, 
sticky.’> Leaves—‘‘Resin (acetone extract) 10.52%; 
Rubber hydrocarbon (benzene extract) 0.77%. Typical 
leaf rubber. ’”’ 
Hevea pauciflora (Spruce ex Benth.) Mueller- 
Argoviensis in Linnaea 84 (1865) 208. 
Brazit: Estado do Amazonas, Rio Negro, Carapana (above conflu- 
ence of Rios Negro and Uaupés). ““Tree 55 feet tall, columnar, 18 
inches in diameter. Latex light yellow, thick, coagulating to a poor 
rubber. Bark externally smooth, light tan-brown, inside whitish, 
thick, hard. Flowers borne before old leaves fall. Staminate flowers 
open cupuliformly, yellow but red line running up centre of sepals 
internally and short red lines at junctions of sepals. Leaflets thick 
chartaceous, horizontal. Seed valves very large.’’ November 30, 1947, 
Richard Evans Schultes & Francisco Lépez 9194. 
At the little hamlet of Carapand, a few kilometers up- 
stream from the confluence of the Negro and the Uaupés, 
there is a small planting of trees of Hevea pauciflora. 
The collection cited above was made from this colony. 
These trees were tapped and an air-dried sample of 
the rubber was submitted to the National Bureau of 
Standards in Washington for analysis. The results of this 
analysis are significant. Dr. Lawrence A. Wood reported 
(Letter and report, Dr. Lawrence A. Wood to Dr. R.D. 
Rands, November 7, 1949) that: ‘*The sample was given 
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