The families of flowering plants.
Habit and leaf form. Shrubs. Leaves small; alternate; spiral (closely crowded towards the branch tips); imbricate; petiolate; simple. Lamina entire; obovate (spathulate);seemingly parallel-veined (see illustration in the original description); seemingly cross-venulate; attenuate at the base. Leaves exstipulate. Lamina margins entire; revolute (and the lamina externally pouched at the apex).
Leaf anatomy. Stomata present; mainly confined to one surface (borne on (confined to?) the inner surface of the pouch); anisocytic.
Adaxial hypodermis absent. The mesophyll without calcium oxalate crystals.
Stem anatomy. Internal phloem present. Secondary thickening developing from a conventional cambial ring. Xylem with vessels. Vessel end-walls scalariform. Wood parenchyma lacking.
Reproductive type, pollination. Plants hermaphrodite. Floral nectaries represented by glands at the bases of the sepals?.
Inflorescence, floral, fruit and seed morphology. Flowers solitary; axillary; fairly showy; regular; (4–)5 merous; cyclic; tetracyclic. Free hypanthium absent. Hypogynous disk absent.
Perianthwith distinct calyx and corolla; (8–)10; 2 whorled; isomerous. Calyx (4–)5; 1 whorled; gamosepalous (basally); regular. Corolla (4–)5; 1 whorled; gamopetalous; lobes imbricate; with a well developed tube; regular.
Androecium (4–)5. Androecial members adnate; all equal; free of one another; 1 whorled. Androecium exclusively of fertile stamens. Stamens 5; inserted near the base of the corolla tube, or midway down the corolla tube (halfway or more down); isomerous with the perianth; oppositisepalous; alternating with the corolla members; filantherous (the filaments quite long, but the anthers enclosed by the corolla). Anthers basifixed; non-versatile; dehiscing via longitudinal slits; latrorse to introrse; tetrasporangiate; appendaged. The anther appendages apical (by extension of the connective into an evident point). Pollen shed as single grains. Pollen grains aperturate; 3 aperturate; colporate.
Gynoecium 2 carpelled. Carpels reduced in number relative to the perianth. The pistil2 celled. Gynoecium syncarpous; synstylovarious to eu-syncarpous; superior. Ovary 2 locular (but the partitions imperfect towards the apex); sessile. Gynoecium stylate. Styles 1; more or less attenuate from the ovary; apical; much longer than the ovary (but included). Stigmas 1–2 (shortly bilobed). Placentation axile (distally intruded-parietal). Ovules30–70 per locule (‘many’); anatropous; unitegmic (the single integument massive); tenuinucellate.
Physiology, biochemistry. Alkaloids seemingly absent. Iridoids ‘apparently’ detected.
Peculiar feature. Laminaexhibiting revolute margins continuous with a characteristic, abaxially pouched tip.
Geography, cytology. Neotropical. Guayana Highland.
Taxonomy.Subclass Dicotyledonae; Tenuinucelli. Dahlgren’s Superorder Gentianiflorae (?); Gentianales (?). Cronquist’s Subclass Asteridae; Gentianales. APG 3 core angiosperms; core eudicot; Superorder Asteranae; lamiid; Order Gentianales (as a synonym of Gentianaceae).
Species 1. Genera 1; only genus, Saccifolium.
General remarks. See Maguire and Pires 1978.