Part 1, 1918] RUBIACEAE 27 
the tube; anthers about 1 mm. long; capsule subdidymous, 3—3.5 mm. wide, about three fourths 
superior, minutely papillose; seeds cymbiform, 1-1.5 mm. long, black, minutely scrobiculate. 
TYPE LOCALITY: West of the Pass of the Limpio, Texas. 
DISTRIBUTION: Western Texas to Arizona, and southward to Veracruz and Puebla. 
4, Houstonia humifusa A. Gray, Proc. Am. Acad. 4: 314. 1858. 
Hedyotis humifusa A. Gray, Bost. Jour. Nat. Hist. 6: 216. 1850. 
Oldenlandia humifusa A. Gray, Pl. Wright. 2: 68. 1853. 
Erect or spreading annual, often forming mats 15 cm. in diameter, usually densely branched, 
the branches slender or stout, scaberulous, the internodes usually shorter than the leaves; 
stipules 2.5 mm. long or shorter, white, copiously setiferous; leaves sessile or the lowest short- 
petiolate, the blades mostly linear, those of the lowest leaves often oblanceolate, 10-15 mm. 
long, 0.6-3 mm. wide, mucronate, scaberulous, the margins more or less revolute; flowers 
axillary, the pedicels very short, recurved after anthesis; hypanthium scaberulous; calyx-lobes 
setaceous-subulate, 3-4 mm. long; corolla slender-funnelform, 6-7 mm. long, pale-purple, 
glabrous outside, the lobes oblong, acute, shorter than the tube, white-papillose inside; cap- 
sule subdidymous, 2.5 mm. broad, about three fourths superior, papillose; seeds cymbiform, 
1.5 mm. long, black, scrobiculate. 
TYPE LOCALITY: Open gravelly banks of streamlets, near Fredericksburg, Texas. 
DISTRIBUTION: Western Texas and southern New Mexico. 
5. Houstonia prostrata Brand. Zoe 5: 105. 1901. 
Houstonia parvula Brand. Zoe 5: 221. 1905. 
Depressed or prostrate annual, much branched, the branches slender, 2-8 cm. long, 
glabrous but minutely whitish-papillose, the internodes longer or shorter than the leaves; 
stipules minute, usually sparsely setiferous; leaves opposite, sessile, or the lowest short-peti- 
olate, the blades linear or linear-oblanceolate, 5-12 mm. long, 0.6—-2 mm. wide, obtuse or 
acute, glabrous, papillose on the upper surface, 1-nerved, the margins often revolute; flowers 
axillary, the pedicels stout, much shorter than the capsules, recurved after anthesis; hypan- 
thium less than 1 mm. long, glabrous; calyx-lobes lance-oblong, acutish, about as long as 
the hypanthium; corolla funnelform, purplish-white, only slightly exceeding the calyx-lobes, 
glabrous outside; capsule subdidymous, 2.5-3 mm. broad, about three fourths inferior, 
minutely papillose; seeds cymbiform, 1.5 mm. long, black. 
TYPE LOCALITY: Near La Palma, Lower California. 
DISTRIBUTION: On sand or gravel beds, Sinaloa and the Cape Region of Lower California. 
6. Houstonia subviscosa (C. Wright) A. Gray, Proc. Am. Acad. 4: 
314. 1858. 
Oldenlandia subviscosa C. Wright; A. Gray, Pl. Wright. 2: 68. 1853. 
Erect annual, 4-15 cm. high, sparsely branched, the branches slender, ascending, short- 
hirtellous with coarse whitish hairs, more or less viscid, the internodes mostly equaling or ex- 
ceeding the leaves; stipules about 0.5 mm. long, scarious, setulose-ciliate; leaves opposite, 
sessile, linear, 5—15 mm. long, 1 mm. wide or narrower, acute, hirtellous and viscid or glabrate, 
the margins revolute; flowers axillary, solitary, the pedicels 3-8 mm. long, filiform, hirtellous 
or glabrate, recurved or refracted after anthesis or rarely only divaricate; hypanthium less 
than 1 mm. long, minutely viscid-hirtellous; calyx-lobes lance-subulate, acute, slightly elon- 
gate in fruit; corolla salverform, 2.5-3 mm. long, white; capsule subdidymous, 2.5—4 mm. 
broad, scabro-hirtellous; seeds cymbiform, rounded-oval, 1 mm. long, minutely scrobiculate, 
black. 
TYPE LOCALITY: Between Lagrange and Lockhart Springs, Fayette County, Texas. 
DISTRIBUTION: Western Texas. 
7. Houstonia Croftiae Britt. & Rusby, Trans. N. Y. Acad. Sci. 7 
10. 1887. 
Spreading annual, much branched, the branches slender, 1—4 cm. long, sparsely hirtellous, 
the internodes equaling or shorter than the leaves; stipules minute, scarious, laciniate-den- 
