FRESHWATER PLANKTON ALGLE FROM CEYLON 
113 
45. Outflow of N. end of tank Kalawewa, 29 Sept. 
4(3. Trincomalie harbour, near commencement of lake Tamble- 
gam, 17 Oct. 
47. Tank Namoluwewa, between milestones 48 and 49 on road 
from Dambulla to Trincomalie, 10 Oct. 
48. Tank Tirappanewewa, 8 Oct. 
49. Small pool near the roadside near Ivekirawa, 30 Sept. 
50. Tank Wendrenkulam, about 1 mile from Kantelai, 14 Oct. 
51. Tank Mahakadawella, 8 Oct. 
52. Tank Mancadawa-wewa, near Ivekirawa, 1 Oct. 
53. River Nalande Oya, near Nalande, 28 Sept. 
54. Outflow of rock-tank near Nalande, 26 Sept. 
55. Tank Tibbotu-wewa, 30 Aug. 
5(3. Tank Borlasgama, near Colombo, 8 Oct. 
57. Tank Ekiniyea-wewa, near Kekirawa, 30 Sept. 
58. Tank Periza-kulam, near Trincomalie, 20 Oct. 
59. Tank Vilankulam, at Yavoniya, 4 Oct. 
60. Lake Tamblegam, 17 Oct. 
61. Small pool (at times a much larger stretch of water) about 
3 miles from Hambantottle, 10 Sept. 
I. CYAR0PHYCE2E. 
The most important constituents of the freshwater plankton of 
Ceylon are evidently the OyancyhycecB. But besides the typical 
limnetic forms such as species of Microcystis, Goelosphcerium, Ana- 
beeno , and certain Oscillatoriaceae, our lists include tycholimnetic 
forms, and the Oscillatoriacese on the average have large fila¬ 
ments of the benthic type. Most of the species recorded are well 
known in the temperate regions, but many favour warmer periods 
here, and their abundance in tropical waters is not surprising. A 
curious feature is the apparent absence of Aphanizomenon, the rarity 
of Gromphos'plueria —a few doubtful colonies, not recorded below, 
being all that was observed of this genus,—and the lack of several 
of the species of Ghroococcus, which are so abundant in temperate 
waters. 
Cliroococcaceae. 
A discussion of the relative taxonomic value of the different 
characters of the Chroococcacese has been given in New Phyt. xii. 
As there has been considerable difference of opinion with regard 
to the limitations of certain species, some attempt has been made to 
enumerate the essential features which a study of the Ceylon 
material has made possible, except in the case of Microcystis, which 
is fully described elsewhere. In many respects we have followed 
Lemmermann in our treatment of the family. 
Chroococcus Naeg. 
This genus evidently does not play such an important part in the 
plankton of Ceylon freshwaters as in that of the lakes of Central 
Europe. A few unidentified species were found besides those recorded 
below, but these were rare. 
Journal of Botany.—Yol. 61. [April, 1923.] 
i 
