Folia dichotoma caulis longis pendulisque rupibus adnatis solummodo puncto. Flores ramulis lateralibus. Stems pendant, attached by expanded (0.2) 0.6 (1.2) cm wide holdfast, central axis (3.6) 17 (41) cm, (0.3) 1.3 (5) mm wide midway between holdfast and first branch, gradually tapering toward apex, circular to somewhat flattened in cross-section, becoming flattened and twisted upon drying; side branches (0.3) 2 (16) cm. Leaves dichotomously-subdichotomously divided, (1.2) 2.4 (7) cm, ultimate divisions parallel sided or awl shaped. Spathella incompletely known. Flowers (2) 7 (44) per side branch, incompletely known. Tepals 3, one on each side of fused stamen filaments, a third between two stamen filaments. Capsules (1.7) 1.9 (2.1) × (0.8) 0.9 (2.1) mm; upper (dorsal) valve (1.6) 1.9 (2) × (0.8) 0.9 (1) mm, (3) 5 (7) ribbed (nonsuture), papillate or papillae indistinct; lower (ventral) valve (1.6) 1.9 (2) × (0.9) 1 (1.1) mm, (7) 7 (9) ribbed (nonsuture). Seeds (0.22) 0.28 (0.41) × (0.14) 0.18 (0.23) mm; (0) 29 (73) per capsule. Discussion: Castelnavia multipartita f. pendulosa is incompletely known. It is documented by three collections, only one of which has leaves and flowers. Two collections consist entirely of dried senescent stems with mature capsules. Phenology: The only specimen examined with flowers was collected in April. Distribution and Habitat: Northwest Mato Grosso and adjacent Pará, Brazil and eastern Bolivia (Fig. 9). Vertical or near vertical surfaces of waterfalls or other areas of especially strong current. In the Teles Pires and Aripuanã Rivers this form occurs in close proximity with C. multipartita f. multipartita. Representative Specimens Examined: BRAZIL. Mato Grosso: Paranaíta, Teles Pires River, 56° 46’41” W, 9° 21’1.8” S, 19 Sep 2007, Bove & Philbrick 1871 (R, WCSU); Aripuanã, Aripuanã River, 56° 27’12.8” W, 10° 9’50.9” S, 23 Sep 2007, Bove & Philbrick 1894 (R, WCSU).