RUBBER (HEVEA) JDISEA&ES 95 
Oryctanthus botryostachys Eichl. Hermaphroditic ; branches erect, fusco- 
furfuraceous or grayish when old, often terminating in leafless floriferous 
racemelike extensions ; internodes 8 to 12 centimeters long ; leaves large, 
elliptically ovate, tips obtuse or attenuate obtuse, base rounded, yellowish 
green, young leaves with brown margin and conspicuous fuscous midrib 
5 to 16 centimeters long by 4 to 8 centimeters broad ; flower spikes soli- 
tary in the axils of the leaves or in terminal racemelike combinations, 
4 to 6 centimeters long ; flowers 15 or more in three to four longitudinal 
rows, peduncles fuscous, 1 to 1.5 centimeters long ; fruit subobovate, yellow- 
ish, sometimes purplish at the base. On Hevea brasiliensis under Bixa 
sp. at Colonia Pedro Borges, Amazonas. Indigo, Per sea gratissima, Bixa 
orelana, and Vernoma sp. are the common hosts. The species is closely 
related to O. amazonicus Ule, but differs in not being bracteolate. 
Phoradendron crassifolkim Eichl. Hermaphroditic ; branches erect, terete, 
occasionally pseudodichotomous, yellowish green, glabrous ; internodes 
usually long, 5 to 12 centimeters ; bracts or cataphyls on the internodes, 
subannular, upper ones more or less deciduous and floriferous, rest sterile ; 
leaves large, elliptically ovate, rarely lanceolate, rounded at the base or 
attenuated along the short petioles, three central nerves usually con- 
spicuous, 4 to 8 or 6 to 10 by 15 centimeters ; flower spikes solitary or 
clustered, axillary or terminal, sometimes compound at the ends of the 
branches, 3 to 5 centimeters long, with 5 to 7 round fusiform joints usually 
bearing 8 to 10 flowers in six series ; peduncle usually bracteolate at the 
base, 4 to 5 millimeters long ; color of flowers not observed ; fruit subglo- 
bose, about 4 millimeters in diameter, greenish yellow. On Hevea brasUi- 
ensis at Riberalta, Bolivia, associated with Siparuna sp. and species of 
Euphorbiaceae, the most common hosts. 
Phthirusa adenostemon Eichl. Monoecious ; branches suberect, terete, only 
slightly compressed in the younger parts, smooth, grayish or greenish gray ; 
internodes 4 to 8 centimeters long; leaves ovate to elliptic, subacuminate, 
coriaceous, smooth, 5 to 7.5 by 2.5 by 3.5 centimeters, middle nerve promi- 
nent, petioles 1 to 1.5 centimeters long; flower spikes solitary or three to- 
gether in the axils of the leaves, simple or compound, terminal one panicu- 
late, subquadrangular to compressed, 5 to 8 centimeters long, secondary 
spikes bracteolate at the base ; flowers white, two to three on short pedun- 
cles, bracteolate, hexagonal and bud shaped when closed, petals six, lanceo- 
late ; fruit not observed. Found once on Hevea brasiliensis associated with 
species of Myrtacea?, the most common host, at Riberalta, Bolivia. The 
species is also common on Anahidea sp. (Bignoniaceae) and Leguminosse in 
the same region. 
P. amazonensis Weir, n. sp. Monoecious; branches long radiculate and 
prehensile, terete, rarely slightly striate, light gray ; internodes 4 to 9 
centimeters long ; leaves thick, coriaceous, smooth, light green, elliptic, 
acuminate, middle nerve conspicuous, 5 to 9 centimeters long, 3 to 6 centi- 
meters broad ; petioles 1 to 1.5 centimeters long; flower spikes solitary in 
the axils of the leaves, simple, paniculate at the tips of the branches, com- 
pressed or subquadrangular, yellowish white, 4 to 9 centimeters long, sec- 
ondary spikes bractless ; flowers 6-parted, red or purplish red, 3 to 4 milli- 
meters long, 1 to 1.5 milUmeters broad, cylindrical in outline and obtuse at 
the top before unfolding; three together, sessile on a short 3-bracteolate 
peduncle ; bracts lanceolate, acuminate ; calyx inconspicuous, acute ; petals 
slightly ridged at the base, lanceolate, curved inwardly at the tips : stamens 
attached to the base of the petals; filaments short, compressed, with con- 
spicuous middle nerve; anthers acuminate, dehiscing by two lateral fiaps: 
style cylindrical, longitudinally striate at the base; stigma capitate-punc- 
tate, dark colored ; ovary depressed ; fruit greenish at base, becoming en- 
tirely yellow or only for half of its length, 4 to 5 millimeters long. Found 
once on Hevea brasiliensis associated with species of Bignoniacese, Solana- 
ceae, and Myrtaceae, the most common hosts, at Riberalta, Rio Beni. Bolivia. 
Type in United States National Herbarium (No. 1,199,133). This species 
has the nature of a vine and may extend along and over the branches of 
the host for considerable distances. 
P. brasiliensis Weir, n. sp. Dioecious; branches erect, entirely terete, gray, 
the last five or six internodes conspicuously ferruginous furfuraceous, 
with occasional glabrous green areas, the rest smooth: internodes 4 to 
5 centimeters long; leaves somewhat fleshy, coriaceous, smooth, deep 
green, margin brown, ovate to elliptic, acuminate, middle nerve on the 
