The Genus Microcystis in Ceylon 
61 
MICROCYSTIS MRUGINOSA Kuetz(4). 
Including var. major Wittr. (see (2)), Fig. a 
Colonies roughly spherical or ellipsoidal, generally clathrate. Cells 
3-7 p, diam., spherical, with pseudo vacuoles. This must be regarded 
as the typical form. The well-known figure of Kirchner( 3 ) does not 
agree with that of Kuetzing( 4 ). It was frequent in all the following 
localities although never reaching the abundance of M. flos-aquce . 
Loc. Tank 1 Andangawa-mahawewa on small jungle footpath 
from Habarane to Sigiri, Oct. nth; tank Balaluwewa, Sept. 29th; 
margin of tank Andankulam, about three miles from Trincomalie, 
Oct. 18th; small pond in Botanical Gardens, Anuradhapoora, Nov. 3rd; 
Rock pool connected with Kalawewa-tank, Sept. 29th. 
MICROCYSTIS FLOS-AQUAE (Wittr.) Kirchner(3) 
Figs, b and c 
Colonies roughly spherical, ellipsoidal or often squarish in optical 
section; not clathrate; cells 3 -yfx diam.; spherical with pseudo¬ 
vacuoles. 
According to Lemmermann ( 5 ) the distinction between this species 
and M. ceruginosa is in its non-clathrate character. Wesenburg- 
Lund( 9 ) on the other hand says that both M. ceruginosa (= Clathro- 
cystis Hansgirg) and M. flos-aquce (= Anacystis Hansgirg) often 
possess clathrate colonies, but that in the latter species this is 
“generally not very noticeable because these colonies have not the 
sharp outlines which the Clathrocystis colonies have with their dis¬ 
tinctly definite covering of slime/’ Wesenburg-Lund, from a study 
of a large amount of material from the Danish freshwater plankton, 
considers that the essential difference between the two species lies 
in (a) the distinctness of the outline of the colonial mucilage, and 
(b) the form of the colonies. He states that the two supposed species 
are connected by numerous transitional stages, and cites an instance 
where a colony had one half with the characters of M. flos-aquce and 
the other half those of M. ceruginosa. In view of the variability of 
these two species he thinks that the numerous species described by 
Lemmermann cannot be upheld. Ostenfeld (6) also argues the identity 
of all the pseudo vacuole-containing species of Microcystis, having 
found transitional forms between M. ceruginosa , M. flos-aquce and 
M. viridis. 
1 The “tanks” in Ceylon are reservoirs of partially artificial origin. In 
them, however, the microorganisms live under normal conditions. 
