Desmids from Thailand and Malaysia

18 M. HIRANO
near the apical part of semicell. Prescott et al. recordded 6-7 undulations. Ruzicka's
figure shows the straight lateral margin without any undulation. Apex of a semicell
shows a somewhat truncate and round shape. St. 26. Europe, N. & S.America. New to
Thailand.
18. Pl. ovatum Nordst. var. ovatum
Krieger 1937, 434, Pl.50, f.1; Prescott et al. 2:1, 1975, 127, Pl.48, f.16; Croasdale &
Flint 1986, 74, Pl.13, f.3,4.
L. 309 ptm, B. 110 ptm. St. 14. India (Bengal), Indonesia (Java), S. America, Austra-
lia, New Zealand, Africa.
18a. var. inermitts M6bius
Scott & Prescott 1961, 17, Pl.6, f.3,4.
L. 295 ptm, B. 106 xtm. and I. 57 ltm. St. 14, Japan, Formosa, S.America, Australia,
Africa.
18b. var. tumidum (Maskell) G.S.West Pl.11, f.4,5,6.
Krieger 1937, 435, Pl.50, f.2,3; Croasdale & Flint 1986, 74, Pl.13, f.5-8.
L. 277-282 ptm, B. 88-90 ptm. Sts. 22,24. India, Burma, Indonesia (Java), Africa,
Australia, New Zealand. New to Thailand.
19. PL raciborskii (Racib.) Croasd.
Prescott et al. 1975, 128, Pl.42, f.1. Syn. Pl. breve Racib. in Krieger 409, Pl.44, f.2.
L. 48.5 #m, B. 15.8 "m. Semicells show the trace of apical spine but other semicell
of the same individual destitute the spine. St. 37. British Guiana. New to Thailand.
20. Pl. rectum Delp. PL5, f.10,11.
Ruzicka 1977, 260, Pl.37, f.3-8; FOrster 1982, 124, Pl.13, f.15.
L. 145-409 ptm, B. 17.5-22 ptm. Cells approximately 13-26 times longer than the
breadth, non attenuated from a basal inflation to the apex, and lateral margin almost
straight except for the basal inflation. Pl. trabecula (Ehrenb.) Ntig. var. rectum (Delp.)
W. & G.S.West is conspecific with this species. Sts. 1,19,30,32,36,40,43,49, Cosmopoli-
tan.
21. Pl. subcoronulatum (Turner) W.West Pl.8, f.2.
Krieger 1937, 422, Pl.46, f.7; F6rster 1982, 125, Pl.15, f.1-2.
L. 268-668 um, B.33-40 ptm. Sts. 25,26,32. India, Burma, Indonesia (Java), Japan,
Africa, Madagascar, Australia, Brazil. New to Thailand.
22. Pl. trabecula (Ehrenb.) Nag. var. trabecula Pl.5, f.8.
West 1904, 209, Pl.30, f.11-13; Krieger 1937, 395, Pl.40, f.1-4.
L. 396-520 ptm, B. 22-35 ptm. Sts. 2,18,19,25,30,44,45,47,49,51,53. Cosmopolitan.
22a. var. crassum Wittr. Pl.5, f.9.
Krieger 1937, 399, Pl.40, f.6; Ruzicka 1977, 268, Pl.38, f.6-7.
L. 220-568 ptm, B. 31-35 ptm. Sts. 17,49. India, Japan, China, Europe, Greenland.
New to Thailand.