herewith reported to Amazonian Colombia greatly am- 
plifies the known distribution of this rare plant. 
In the small creeks and rills forming in the headwaters 
of the Rio Piraparana, Thurnia sphaerocephala grows in 
extraordinary abundance in the shallow waters, together 
with a species of Pontederia. It often grows so thickly 
that it impedes canoe travel completely. This habitat is 
unusual, for the type and numerous later collections of 
the species from British Guiana report the habitat as 
‘*savannahs. *’ 
Ihave seen Thurnia sphaerocephala, but did not collect 
it, in Cano Paca, one of the rills forming the headwaters 
of the Rio Papuri, and in the very sources of the Rio 
Dji. Both the Papuri and the Dji, rising in an area near 
the headwaters of the Rio Piraparand, are affuents of 
the Rio Vaupés. 
The westernmost locality of the family is that of 
Schultes & Cabrera 19853, in the headwaters of the Cano 
Churruco, a brook of clear water, draining a quartzitic 
area. It is not abundant, however. 
Cotompia: Comisarias del Amazonas-Vaupés, Rio Apaporis, Sora- 
tama (above mouth of Rio Kananari) and vicinity, Cafio Churruco, Alt. 
about 900 feet. General location: Lat. 0°5’ N, Long. 70°40’ W. “‘In 
water.’’ January 1952, Richard Evans Schultes & Isidoro Cabrera 19588. 
—Comisaria del Vaupés, Rio Piraparana (tributary of Rio Apaporis), 
Cafio Paca. General location between Lat. 0°15’ S, Long. 70°30! W 
and Lat. 0°25’ N, Long. 70°30’ W. September 19, 1952, Richard 
Evans Schultes & Isidoro Cabrera 17568. 
RAPATEACEAE 
Schoenocephalium Martianum Seubert in Mar- 
tius Fl. Bras. 8, pt. 1 (1847) 130, t. 19. 
The curious and beautiful genus Schoenocephalium was 
based on material collected at Araracuara on the Rio 
Caqueta, Colombia, by Martius in 1820. Two species 
were described: Schoenocephalium Martianum and 8. 
arthrophyllum. 
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