0.18%, “typical leaf rubber”. Schultes et Lopez 9663: (bark) res- 
ins 4.24%, rubber hydrocarbons 0.83%, “sticky and weak, not 
near the quality of above sample”; (leaves) resins 13.65%, rubber 
hydrocarbons, 0.21%, “typical leaf rubber”. For M. Spruceana 
(Schultes et Lopez 9641), the following results were recorded for 
bark rubber: Resins 3.92%, rubber hydrocarbons 1.31%; “poor, 
soft, sticky.” Micrandra Sprucei (Schultes et Lopez 9640) gave 
the following data: (bark) Resins 5.63%, rubber hydrocarbons 
5.51%, “poor, soft and sticky”; (leaves) resins 16.84%, rubber 
hydrocarbons 0.16%, “typical leaf rubber.” 
An analysis of specimens sent in from Venezuela (probably by 
one of the expeditions the reports of which are quoted above) 
had a rubber content of 85.74 (Polhamus, L. G.: “Rubber con- 
tent of miscellaneous plants” U.S.D.A. Prod. Research Dept., 
No. 10 (1957) 22). The species from which the sample was taken 
is stated to have been Micrandra siphonioides, but this identifi- 
cation is open to some doubt. If the specimen were collected by 
either Fuller or Hansen who prepared the reports, its prov- 
enience was more probably Micrandra minor: the trees grew “in 
low land flooded annually” and “close to rivers... rarely at 
distances greater than 300-400 yards”: this is precisely the habi- 
tat of M. minor, not of M. siphonioides. 
A somewhat more complete chemical study appeared in 1956 
(Wisniewski, A.: “Borrachas amazOnicas pouco conhecidas” in 
Bol. Tecn. Inst. Agron. Norte 31 (1956) 301) in which, nonethe- 
less, the author confessed to a lack of knowledge of Micrandra 
rubber in general. Wisniewski’s samples were air-dried. He had 
an average of five samples, and he compared Micrandra rubber 
to a piece of Acre Fina (the highest grade of rubber from Hevea 
brasiliensis) in the following summary: 
CR kg./cm.? AM Resin 
Micrandra 266 760 4.86 
Acre Fina 210 805 2.53 
