Ascogrammitis dilatata (Sundue & M.Kessler) Sundue
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Authority
Sundue, Michael A. 2010. A monograph of
, a new genus of grammitid ferns (Polypodiaceae). Brittonia. 62 (4): 357-399. -
Family
Polypodiaceae
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Scientific Name
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Description
Description - Plants epiphytic, singular or forming small colonies; roots non-proliferous; rhizome ca. 1.5 mm wide; branch buds absent; rhizome scales 1.5-3x0.2-0.3 mm, lanceolate, the cell walls dark red, the lumina iridescent, trans- parent to partially occluded, the apex attenuate, the margins setose, the setae 0.2 mm long, reddish, the surface glabrous; fronds 21-27 x 2-5 cm, hemidimorphic, arching to pendent, usually bearing the mycelia and ascomes of Acrospermum; petioles 4- 12 cm x 0.5-1 mm, with a single vascular bundle, distally marginate, castaneous, very sparsely setose, the setae 0.5-1 mm, sparsely hairy, the hairs 1 -furcate; rachis with casta- neous sclerenchyma visible on both sides of the lamina, the abaxial side very sparsely setose, the setae 0.5-1 mm, sparsely hairy, the hairs 1 -furcate, 0.1 mm long, the adaxial side moderately setose, the setae 0.5-0.7 mm long; laminae 1 -pinnatisect throughout, char- taceous, the base attenuate, with 4-8 pairs of reduced segments the basal segments widely spaced but narrowly connected, apparently never fully pinnate; medial segments 1.5- 2.5 cm x 2.5-4 mm, slightly ascending, narrowly triangular to oblong, the base expanded, decurrent and surcurrent, the apex acute, the margins sparsely provided with simple, two-celled hairs, ca. 0.1 mm long, or sometimes the hairs replaced irregularly by setae, 0.5 mm long, rarely the margins regularly setose; the abaxial lamina surface glabrous to sparsely provided with 0.1 mm long simple hairs and 0.5 mm long setae, the fertile portions of the lamina more densely setose, the adaxial surface of the lamina with scattered setae along the segment costae, the setae 0.5 mm long; segment costae with castaneous sclerenchyma visible on both sides of the lamina; veins not readily visible on either side of the lamina; hydathodes cretaceous, the secretion often abraded; sori inframedial, up to 12 pairs per segment, confined to the distal portion of the lamina; receptacular setae present.
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Discussion
Ascogrammitis dilatata can be distinguished by its 1 -pinnatisect laminae and dilated segment bases that are both strongly decurrent and surcurrent. The basal segments are usually remote from each other and the lamina tissue connecting these segments is very narrow, ca. 0.2 mm wide. Some specimens, primarily from the northern portion of its range, have longer hairs (ca. 0.2 mm) along the segment margins and some of these hairs are replaced by 0.5 mm long setae. Ascogrammitis dilatata was originally described from specimens referred to as A. david-smithii, but that species differs by having fully 1 -pinnate laminae, and segments that are parallel-sided, not expanded at the base. Ascogrammitis david-smithii further differes by the setae of the abaxial lamina distributed evenly, versus confined to sori and fertile veins in A. dilatata.
Lellingeria carrascoensis is also placed here in synonymy. The type, De Boer, M. 1161, was included as a paratype in the protologue of A. dilatata (Sundue & Kessler, 2008). It does not belong in Lellingeria as evidenced by the presence of setae, 1 -furcate hairs along the petiole and rachis that lack an acicular cell, and rhizome scales with reddish instead of hyaline marginal setae. It also has pinna costae with dark sclerenchyma visible on the lower surface and cretaceous hydathodes - two uncommon characters in Lellingeria. Chloro- plast sequence data further support its place- ment in Ascogrammitis (Sundue et al, in press)