While there is a possibility that yoco comprises several 
species, the only one known to be used in the Putumayo 
among the Inga, Siona and Kofin Indians represents an 
undescribed species of the sapindaceous genus Paullinia 
which is herewith described. It has been thought appro- 
priate to employ as a specific epithet the common name 
by which the plant is known in the area where its use as 
a stimulant is practiced, 
IT. Description of yoco 
Paullinia Yoco Schultes & Killip sp. nov. 
Frutex scandens, extensus, robustusque. Rami ro- 
busti, basi usque ad 12 em. in diametro, lactiferi, lacte 
albo astringentique, nigro cum cortice lenticellato scab- 
roque. Ramuli subteretes, obtuse angulati et  fibroso- 
striati, ferruginei, scabridiusculi, minute pulverulento- 
puberuli denique subglabrescentes, internodiis brevibus, 
pampinis robustis frequentibusque, circinalibus, denique 
valde crasso-ligneis. Folia plerumque quinque-pinnata, 
usque ad 85 cm. (rarissime usque ad 45 em.) longa, fere 
aequaliter lata. Rhachides nudae, (exalatae), firmae, levi- 
ter fibroso-striatae, ferrugineae, parce puberulae, 6—20 
em. longae, 2-8 mm. in diametro, quattuor-sulcatae. 
Foliola majora, elliptica, 15-25 (plerumque plus minusve 
20) cm. longa, 8-11 cm. lata, superiora plus minusve ob- 
ovata, apice breviter acuminata acumine obtuso, margine 
integerrima, coriaceo-chartacea, utrinque glabra, subses- 
silia (petiolis nudis, usque ad 5 mm. longis, plus minusve 
2mm. in diametro), viva utrinque atroviridia, subtus niti- 
da (in sicco flavo-fulva), clathrato-venosa, lateralibus cum 
nervis septem ad novem supra impressis subtus prominen- 
ter et valde elevatis, nervo praecipuo utrinque minutis- 
sime scabridiusculo-puberulo. Thyrsi solitarii, sparsissime 
et minute pulverulento-puberuli, robusta cum rhachide 
7-25 (plerumque 10-15) cm. longa et 8 mm. in diametro, 
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