Taxon Details: Megalastrum sparsipilosum R.C.Moran & J.Prado
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Family:
Dryopteridaceae (Pteridophyta)
Dryopteridaceae (Pteridophyta)
Scientific Name:
Megalastrum sparsipilosum R.C.Moran & J.Prado
Megalastrum sparsipilosum R.C.Moran & J.Prado
Description:
by: R.C. Moran, J. Prado
Type: Mexico. Chiapas: Mun. Yajalón, steep slopes of Ahk'ubal Nab above Yajalón, 17°13'N, 92°19'W, 1200 m, 6 Apr 1973, D. E. Breedlove 34621 (Holotype: NY-2 sheets; isotypes: F, MO).
Description: Rhizomes to 0.4 m tall; leaves up to 4.6 m long; scales of the petiole base 20-50 × 2-3 mm, linear-lanceolate, spreading, golden to yellowish brown, denticulate throughout; laminae up to 3 m long, 4-pinnate-pinnatisect at base, medially 3-pinnate-pinnatisect; basal pinnae ca. 1 m long, strongly inequilateral (elongated basiscopically); pinna rachises abaxially sparsely glandular, sparsely scaly, glabrous to sparsely pilose, the glands ca. 0.1 mm wide, spherical, brownish, the scales to 2-3 × 0.2-0.5 mm, linear to lanceolate, appressed to slightly spreading, strongly denticulate, the hairs 1.0-1.5 mm long, ca. 8-celled, adaxially glandular, densely pilose, the glands ca. 0.1 mm wide, spherical, sessile, brownish, the hairs 1-2 mm long, 7-9-celled, spreading, light brown, the scales like those abaxially; costules abaxially sparsely glandular, sparsely pilose to nearly glabrous, sparsely scaly, the hairs 1.5-2.0 mm long, 8-12-celled, erect, the scales 0.8-1.0 mm long, strongly denticulate, appressed to slightly spreading, reddish brown, slightly shiny, the scales like those on the pinna rachises, proscales numerous, appressed, adaxially with indumenta like that of the pinna rachises; laminar tissue between the veins abaxially non-glandular, glabrous, adaxially sparsely glandular to nearly non-glandular; veins on both surfaces visible, abaxially non-glandular, sparsely pilose, the hairs 0.5-0.7 mm long, 3- or 4-celled, adaxially pilose, sparsely glandular, the hairs 1.0-2.0 mm long, 3-8-celled, spreading, the glands sessile, spherical; hydathodes evident; lamina margins sparsely ciliate to nearly glabrous, the hairs 0.2-0.4 mm long, 2-4-celled, non-glandular; indusia minute, fugacious, apparently consisting of a cluster of reddish proscales, ca. 0.1 mm long, protruding from the center of the sorus.
Distribution: Mexico, Honduras; cloud forests, wet forests, montane rain forests, 1200-2800 m.
Comments: Megalastrum sparsipilosum is characterized by leaves to 4.5 m long, laminae sparsely pilose on both surfaces, and strongly denticulate scales on the axes abaxially. It resembles M. heydei and M. pulverulentum in large size and leaf dissection. Megalastrum sparsipilosum differs from the former by longer hairs on both surfaces of the pinna rachises (these hairs 0.1-0.2 mm long in M. heydei), and from the latter by sparsely pilose pinna rachises, costules, and veins on abaxial surface of the laminae (versus densely pubescent on these parts in M. pulverulentum). The specific epithet sparsipilosum refers to the sparse pubescence on the abaxial surface of the laminae, especially when compared to the similar M. pulverulentum. Specimens of Megalastrum sparsipilosum from Chiapas and Guatemala are more sparsely pubescent than those from Honduras. In some, it is difficult to find hairs on the lamina margins-a characteristic unusual in the genus. The variation in pubescence does not appear to correlate with other characters and is therefore interpreted here as variation in a single species.
by: R.C. Moran, J. Prado
Type: Mexico. Chiapas: Mun. Yajalón, steep slopes of Ahk'ubal Nab above Yajalón, 17°13'N, 92°19'W, 1200 m, 6 Apr 1973, D. E. Breedlove 34621 (Holotype: NY-2 sheets; isotypes: F, MO).
Description: Rhizomes to 0.4 m tall; leaves up to 4.6 m long; scales of the petiole base 20-50 × 2-3 mm, linear-lanceolate, spreading, golden to yellowish brown, denticulate throughout; laminae up to 3 m long, 4-pinnate-pinnatisect at base, medially 3-pinnate-pinnatisect; basal pinnae ca. 1 m long, strongly inequilateral (elongated basiscopically); pinna rachises abaxially sparsely glandular, sparsely scaly, glabrous to sparsely pilose, the glands ca. 0.1 mm wide, spherical, brownish, the scales to 2-3 × 0.2-0.5 mm, linear to lanceolate, appressed to slightly spreading, strongly denticulate, the hairs 1.0-1.5 mm long, ca. 8-celled, adaxially glandular, densely pilose, the glands ca. 0.1 mm wide, spherical, sessile, brownish, the hairs 1-2 mm long, 7-9-celled, spreading, light brown, the scales like those abaxially; costules abaxially sparsely glandular, sparsely pilose to nearly glabrous, sparsely scaly, the hairs 1.5-2.0 mm long, 8-12-celled, erect, the scales 0.8-1.0 mm long, strongly denticulate, appressed to slightly spreading, reddish brown, slightly shiny, the scales like those on the pinna rachises, proscales numerous, appressed, adaxially with indumenta like that of the pinna rachises; laminar tissue between the veins abaxially non-glandular, glabrous, adaxially sparsely glandular to nearly non-glandular; veins on both surfaces visible, abaxially non-glandular, sparsely pilose, the hairs 0.5-0.7 mm long, 3- or 4-celled, adaxially pilose, sparsely glandular, the hairs 1.0-2.0 mm long, 3-8-celled, spreading, the glands sessile, spherical; hydathodes evident; lamina margins sparsely ciliate to nearly glabrous, the hairs 0.2-0.4 mm long, 2-4-celled, non-glandular; indusia minute, fugacious, apparently consisting of a cluster of reddish proscales, ca. 0.1 mm long, protruding from the center of the sorus.
Distribution: Mexico, Honduras; cloud forests, wet forests, montane rain forests, 1200-2800 m.
Comments: Megalastrum sparsipilosum is characterized by leaves to 4.5 m long, laminae sparsely pilose on both surfaces, and strongly denticulate scales on the axes abaxially. It resembles M. heydei and M. pulverulentum in large size and leaf dissection. Megalastrum sparsipilosum differs from the former by longer hairs on both surfaces of the pinna rachises (these hairs 0.1-0.2 mm long in M. heydei), and from the latter by sparsely pilose pinna rachises, costules, and veins on abaxial surface of the laminae (versus densely pubescent on these parts in M. pulverulentum). The specific epithet sparsipilosum refers to the sparse pubescence on the abaxial surface of the laminae, especially when compared to the similar M. pulverulentum. Specimens of Megalastrum sparsipilosum from Chiapas and Guatemala are more sparsely pubescent than those from Honduras. In some, it is difficult to find hairs on the lamina margins-a characteristic unusual in the genus. The variation in pubescence does not appear to correlate with other characters and is therefore interpreted here as variation in a single species.