224 



Dr. F. E. Fritsch. On the Subaerial and [Jan. 2, 



dissolved oxygen in the water ; periodic (often rapid) change of water-level, 

 causing exposure for the attached forms of the higher zones and change in 

 concentration of the water for the forms of the lower zones ; mostly a muddy 

 or clayey substratum with occasional rocks (detached from the dams) ; water 

 which is generally almost stagnant. 



Looking upon the algal flora of the tanks in its entirety (we may even 

 for a moment include the Plankton in these remarks), one is struck by 

 the fact that in a considerable number of them it is completely dominated 

 by the blue-green element.* The table below may serve as an illus- 

 tration of this point ; the various tanks studied are classified in three 

 series according to the composition of Benthos and Plankton. Those tanks 

 of the first series which are provided with an asterisk contain practically 

 nothing but Cyanophycese ; the remainder have a noticeable green element* 

 although still entirely dominated by the blue-green. It also seems of 

 interest to notice the relative amounts of Phanerogamic vegetation present ; 



Table to show Essential Composition of Algal Growth in Ceylon Tanks. 



Littoral growth, blue -green. 



Plankton only, blue-green. 



Plankton, green. 



Plankton, blue-green. 



Littoral growth, green. 



Littoral growth, green. 



Colombo Lake (!). 



Villamkulam. 



Pond in Peradeniya 



Kandy Lake (!). 



Tirappanewewa.f 



G-ardens. 



Nuwarawewa. 



Balaluwewa. 



^ fKelawewa.J 



"o | Mancadawewaf (animals 



% f Tissawewa (!). 



Periyakulam (near Trin- 



"o Basawakkulam. 



comalie) . 



a J common). 



o I Punchikekirawa.J 



a J *Tank in Anuradhapoora 





o | Gardens. 





S Ekiniyeawewa.f 

 ■g (^Malawewewa.f 



£ | *Town tanks, Anuradha- 





■g t_ poora. 





M BalankulamJ (near Anu- 



M Madokotaikulam (near Va- 





radhapoora). 



voniya). 

 Madawachyawewa. 





Madakanawewa.J 

 Mahakadawellawewa. 





# Dambullawewa (!) 



Littoral growth only, 



Namoluwewa. 



(Plankton only !) . 



blue -green. 



Megaswewa (!)f (Plankton 



*Neravieawewa (!). 



Plankton, green. 



only!). 



Habaranewewa (!) 

 (Plankton only!). 





Wendrenkulamf (Plankton 

 only!). 





Tank at Sigiri. 



Nalandewewa (!)f. 



Kurunegalawewa (Plankton 



*Pokuna on top of rock 



Walikulam (near Keki- 



only!). 



Sigiri (!) (Plankton 



rawa). 



Senadiniyagawawewa (!) 



only!). 



Karambawewewa. 



(near Habarane) (Plank- 



Lake Mineri. 



Yaka-anaguhuwewa (near 



ton only !). 



*Lake Kantelai. 



Habarane). 



Borlasgamawe wa . J 



*Andankulam. 



Mahakekirawa. 



Tibbotuwawewewa. 



Hiriwadunnawewa (near 



Kekunadurewewa (!)f. 



Koilpuliumkulam (near 



Habarane). 





Vavoniya). 

 Malawewewa.J 



* I, of course, exclude the green Phanerogamic vegetation, which is often abundantly 

 developed in tanks which are otherwise completely dominated by the blue-green forms, 

 t Plant life very poorly represented. 

 X With a noticeable admixture of blue-green forms. 



