Wagner, Warren L., Derral R. Herbst and S. H. Sohmer. 1999. Manual of the Flowering Plants of Hawai'i (Bernice Pauahi Bishop Museum Special Publication, 2 Vol. Set). Honolulu, HI

Flora of Hawaii:

Distribution     
In the Hawaiian Islands, endemic to Hawai`i.

Habit
Scandent vines; stems densely retrorsely strigose, more sparsely so with age. 

Leaves
Leaves thick, narrowly ovate, 7.5-14 cm long, 2.5-5 cm wide, very densely silky strigose, margins serrate, apex acute to short-acuminate, base broadly cuneate to truncate, petioles 1.7-3.5 cm long, densely antrorsely strigose.  Flowers  

Flowers
Flowers 6-10 per verticillaster, in compact, unbranched, racemose inflorescences ca. 10-15 cm long, pedicels 3-10 mm long, densely shaggy villous, bracts narrowly lanceolate to lanceolate, 10-20 mm long, lowermost pair largest, ca. 20-40 mm long, bracteoles of individual flowers conspicuous, linear-deltate, ca. 3-4 mm long; calyx campanulate, 6-7 mm long, densely antrorsely long-strigose, the teeth deltate, 1-2 mm long, apex acute, slightly thickened; corolla white, tube slightly curved, ca. 12 mm long, densely antrorsely strigose throughout, upper lip ca. 5-7 mm long, lower lip ca. 8-10 mm long.   

Fruit
Nutlets ca. 4-5 mm long. 
 
Chromosomes
2n = ca. 66*