Arachnandra Barfuss, Leme & W. Till, 2025

Arachnandra Barfuss, Leme & W. Till , gen. nov.

Diagnosis:—This new genus differs from Alcantarea , Stigmatodon , Vriesea , and Waltillia by its unique combination of morphological characters, such as sepals lanceolate-acuminate, petals distinctly appendaged, 3.8–4.6 times longer than wide, forming an open, fan blade-like corolla, stamens radially arranged, prostrate, pollen subglobose, sulcus broad, without prominent ornamental elements, margins weakly distinct, stigma of the conduplicate-patent type, and seeds with a basal appendage distinctly longer than the inconspicuous apical appendage.

Type:— Tillandsia drepanocarpa Baker.

Description:— Plants epiphytic. Leaves thin in texture, forming water impounding rosettes; leaf sheath distinct; leaf blade narrowly lanceolate, acuminate. Inflorescence compound, with short, inconspicuous branches. Flowers diurnal, strongly fragrant, divergent to slightly secund; sepals lanceolate, acuminate, subsymmetrical; petals spathulate, 3.8– 4.6 times longer than wide, connate at the base, spreading to reflexed, forming an open, fan blade-like corolla, bearing 2 linear or narrowly lanceolate appendages; stamens shorter than the petals but exposed by the reflexed petals, radially disposed, prostrate; filaments terete, adnate to the petal tube and free above it; anthers linear, the pollen sacs with a prevailingly frontal line of dehiscence, connective area exposed and not covered by the margins of the pollen sacs; pollen subglobose, ca. 55 µm in diameter, sulcate, the sulcus broad, without ornamental elements, margins moderately distinct, with small exine elements attached; ovary almost totally superior or not more than 1/8 inferior (considering the nectary tissue), placentation totally superior; stigma of the conduplicate-patent type, white. Fruits a septicidal capsule; seeds with an umbrella-like, plumose basal coma distinctly longer than the straight, undivided inconspicuous apical appendage.

Species:— Arachnandra is a monotypic genus.

Etymology: —From classical Greek “Arachné” = spider, and “andra” = man (male), referring to the spider-like arrangement of the stamens lying on the corolla.

Distinctive characters:— Arachnandra is a member of tribe Vrieseeae , subtribe Vrieseinae , being closely related to Alcantarea , Stigmatodon , Vriesea and Waltillia . However, this new genus differs from Alcantarea by its general small size when in bloom ( vs. usually large sized), flowers distinctly smaller ( vs. flowers large), sepals with acuminate apex ( vs. obtuse), petals 3.8–4.6 times longer than wide, spathulate ( vs. 10 to 15 times longer than wide, linear or nearly so), pollen with sulcus margins moderately distinct [ vs. sulcus margins sharply cut, “ Alcantarea type ”)], and seeds with a long appendage at the basal end and an inconspicuous appendage at the apical end ( vs. with a short appendage at the basal end and a long appendage at the apical end).

In relation to Stigmatodon , Arachnandra can be distinguished by leaves mesomorphic ( vs. semi-xeromorphic to xeromorphic), leaf blades sparsely and inconspicuously lepidote, margins not truncate ( vs. densely and conspicuously lepidote, margins often truncate), inflorescence with inconspicuous lateral branches exceeded by the primary bracts ( vs. simple or paniculate with large lateral branches much exceeding the primary bracts), flowers diurnal ( vs. flowers nocturnal), petals much narrower, spreading to reflexed at anthesis, forming an open, fan blade-like corolla ( vs. much broader, suberect and forming a campanulate corolla), petals bearing narrower, linear to lanceolate appendages ( vs. bearing much broader appendages), stamens radially arranged, prostrate ( vs. usually with three of them disposed in each lateral sides of the corolla), pollen globose, the sulcus broad, without ornamental exine elements [ vs. ellipsoid, sulcus narrower, covered with exine elements separated from each other, forming isolated exine islands (‘insulae type’, “subtype d”)], and stigma of the conduplicate-patent type, white, densely papillate ( vs. of the tubo-laciniate types I and II or convolute-blade type III, green or greenish, without papillae or sparsely papillate).

In comparison with Vriesea , it differs by flowers strongly fragrant despite diurnal ( vs. odorless when diurnal or scented in night-blooming, usually bat pollinated species), sepals acuminate ( vs. mostly obtuse, rounded, and emarginate, rarely acute or acuminate), petals white, spreading to reflexed at anthesis, forming an open, fan blade-like corolla ( vs. yellow, often with green tips, cream, brownish-red or rarely white, usually erect in diurnal species, except for the suberect to recurved apex, forming a prevailingly tubular corolla, or corolla campanulate in night blooming species), pollen globose, sulcus broad, without ornamental exine elements [ vs. ellipsoid, sulcus narrower, covered with exine elements separated from each other, forming isolated exine islands (‘insulae type’, “subtype d”)], and stigma of the conduplicate-patent type ( vs. of the convolute-blade II type).

Arachnandra is also related to Waltillia , differing by leaves mesomorphic, forming water impounding rosettes ( vs. semi-xeromorphic, forming non-water-impounding rosettes), flowers smaller, diurnal ( vs. flowers larger, nocturnal), sepals acuminate ( vs. obtuse to emarginate), petals connate at the base, white, spreading to reflexed at anthesis, forming an open, fan blade-like corolla ( vs. free, pale greenish-yellow, forming a campanulate corolla), petals bearing well developed appendages ( vs. unappendaged), pollen sulcus without ornamental exine elements ( vs. sulcus covered by a kind of operculum of almost smooth exine elements with some perforations), stigma of the conduplicate-patent type ( vs. of the convolute-blade II type), seeds with a long appendage at the basal end and an inconspicuous appendage at the apical end ( vs. with a short appendage at the basal end and a long appendage at the apical end).