Herbs, often with dense growth. Stems of two types: 1) prostrate and 2) petiolar (epiphyllous; arising from leaf petioles); prostrate stems tightly attached to substratum throughout, cylindrical to flattened in cross-section, (0.9) 2 (3) mm wide, repeatedly dichotomously or subdichotomously branched; petiolar stems unattached to substratum, (2) 4 (6) times dichotomously or subdichotomously branched, usually curled, projecting (2.5) 7 (20) mm from petioles. Leaves aris- ing from stem margins, simple when young, pinnately lobed or pinnately compound when mature; simple leaves linear to spatulate, (0.3) 1.5 (13) × (0.2) 0.4 (0.8) mm, spatulate upper regions (0.2) 0.6 (1.2) mm wide; pinnate leaves (1.7) 13 (22) × (0.4) 1.3 (6) cm; petiolate, petiole round to elliptical in cross- section, (0.8) 3.2 (8) cm; rachis distinctly widened and flattened, (1.4) 4.7 (12) mm wide, (2) 5 (12) veined; pinnae (0.2) 1.5 (9) cm long, variously lobed, ultimate lobes (0.2) 2.1 (8) × (0.1) 0.3 (0.8) mm, linear, spatulate or triangular in outline, apex acute or obtuse. Spathella (1.9) 2.6 (3) × (1) 1.4 (1.7) mm, rupturing apically or subapically into (5) 7 (11) linear to trian- gular segments. Flowers numerous [few postanthesis flowers observed], lateral on stems or axillary to branches, each in a cavity; pedicel (0.4) 0.5 (0.7) mm prior to anthesis. Tepals 2, hair-like, one on each side of fused stamen filaments, (0.1) 0.3 (0.5) mm, apex acute. Stamens 2, filaments (0.9) 1.4 (1.9) × (0.6) 0.8 (1.2) mm prior to anthesis, elongating and projecting from ruptured spathella during anthesis; anthers (0.6) 0.8 (1) × (0.3) 0.4 (0.6) mm. Pollen polar diameter (16.2) 17.6 (18.8) μm, equatorial diameter (17.5) 19.1 (20) μm, sexine 0.6 μm, nexine 0.8 μm. Ovary in preanthesis flowers (1.3) 1.8 (2.6) × (0.9) 1.1 (1.6) mm. Ovules (93) 132 (147) per ovary. Stigmas (0.1) 0.4 (0.6) mm prior to anthesis, elongating to (0.7) 1 (1.6) mm dur- ing anthesis. Capsules (1.5) 1.8 (1.9) × (0.8) 1.3 (1.6) mm; upper (dorsal) valve (1.1) 1.6 (1.9) × (0.7) 0.9 (1.2) mm, 5 ribbed (non- suture), lacking papillae; lower (ventral) valve (1.3) 1.6 (1.8) × (1) 1.3 (1.6) mm, 7 ribbed (nonsuture). Seeds (0.17) 0.22 (0.26) × (0.12) 0.15 (0.18) mm; (0) 77 (124) per capsule. Discussion:
Jäger et al. (2016) report that expanded leaf-like structures that occur on Castelnavia noveloi are leaf-like roots. In their monograph of the genus, Philbrick et al. (2009) describe them as leaves. [Jäger-Zürn, I., C. T. Philbrick & C. P. Bove.2016. The architecture of Castelnavia noveloi (Podostemaceae) – a re-investigation.Brittonia 68: 202-211.DOI 10.1007/s12228-016-9408-6]
Phenology: Flowering May-June. Distribution and Habitat: Castelnavia noveloi is known only from the Taquarussu River, east of Taquarussu, Tocantins, Brazil (Fig. 9). The plant has been collected along approximately 0.5 km of the river and is interpreted as vulnerable (IUCN 2001). Plants occur on large outcrops across which water flows. Castelnavia noveloi occurs with two other species of Podostemaceae: Monostylis capillacea Tul. and Apinagia sp. Representative Specimens Examined: BRAZIL. Tocantins: Taquarussu, Taquarussu River, 48° 10’15.3” W, 10° 18’13.2” S, 26 Jul 2006, Philbrick et al. 6000 (R, WCSU).