Desmids from Thailand and Malaysia

15.
16.
L
2.
3.
Desmids from Thailand and Malaysia 67
rectis; semicellulae in vertice visae angusto rhomboidae, lateribus convexis, polis obtusis
cum spinis longis. Long. 40 ptm, lat. 70.4 ptm, lat. isthm. 13.2 ptm. St. 43. Thailand.
Type: Pl.32, f.7; Pl.33, f.10. Loc. Botanical Garden, Chiengmai, Thailand.
Cells large, approximately 1.6 times broader than the length without spines, deeply
constricted, sinus acutely open; semicells broadly subtriangular, apex convex, apical
angles with a Iong, stout, incurved, downward-directed spine, lateral margin (lower
lateral margin) almost straight; semicells in a vertical view narrow-rhomboidal, lateral
margin convex, poles obtuse and with a Iong spine. L. 40 ptm, Bssp. 70.4 ptm, and I.
13.2 ptm. St. 43.
A. triangularts Lagerh. Pl.33, f.5.
West 1911, 4, 97, Pl.114, f.11-13,17.
Lssp. 23-30 ptm, B. 19-25 xtm, and I. 5-7#m. Sts. 18,19. Burma, Japan, Europe,
U.S.A., Brazil. New to Thailand.
A. validus (W.&G.S.West) Scott&GrOnblad Pl.31, f.3.
Scott & Gr6nblad 1957, Act. Soc. Sci. Fenn. II.B. 218, 29, Pl.17, f.16; Prescott et al.
1982, 2:4, 37, Pl.301, f. 10,12,13.
L 26-27 ptm, B. 24-26.4 ptm, and I. 4.5-11 #m. Sts. 36.40,41. N. & S.America,
Africa. New to Thailand.
Staurastrum abruptum W.&G.S.West Pl.49, f.3,4.
W. & G.S.West 1896, Trans. Linn. Soc. Bot. 5, 256, Pl.16, f.13; Prescott et al. 1982,
2:4, 116, Pl.329, f.6.
L. 33 xtm, B. 19.8 ptm, and I. 5.3 xtm. Cells small, slightly broader than the length,
deeply constricted, sinus open and acute; semicells subhexagonal, apex truncate and
slightly retuse, apical angles broadly rounded, lateral margin slightly convex, lower later-
al margin almost straight, semicells in vertical view triangular, apex convex and truncate,
side view concave. St. 20. N. America. New to Thailand. This species from Thailand
seems to be larger in size than that of the American forms.
St. acanthastrum W. &GS.West Pl.43, f.1,2; Pl.48, f.1,2.
West 1902, Trans. Linn. Soc. Bot. 6, 183, Pl.22, f.1; Hirano 1959, Contr. Biol. Lab.
Kyoto Univ. 9, 372, Pl.48, f.6,11; Scott & Prescott 1961, 85, Pl.42, f.1.
L. 31 xtm, Bcpr. 79 ptm, and I. 8.8 "m. Cells large, 5-radiate, deeply constricted at
the middle, sinus open and acuminate at the extremity; semicells subglobose or fusiform,
apex convex, angles produced into long, horizontal process, undulate and tapering to the
apex, with 3 sharp spines disposed; vertical view of a semicel 5-radiate, processes long,
tapering nodulated and 3 sharp spines at the extremity, body of a semicell with a ring of
a pair of verucae at the base of process. Sts. 2,25,27. Ceylon, Indonesia (Java), Japan.
New to Thailand.
St. acanthocephalum Skuja Pl.42, f.10.
Skuja 1949, Nov. Act. Reg. Soc. Sci. Upsal. IV, 14:5, 151, Pl.34, f.25; Scott & Pre-
scott 1961, 85, Pl.52, f.5,6.