244 Fritsch . — The Subaerial and Freshwater 
blue-green vegetation. As a general rule the smaller the dimensions of a tank 
the less pronounced is the blue-green element found to be. In other types 
of Ceylon freshwaters the dominance of the Cyanophyceae was equally 
pronounced (rock-pools and, to a less extent, the rice-fields) or not so marked 
(small pools and ditches, and especially wells). The prevalence of this group 
is no doubt, again, due to the high temperature of the water and the intensity 
of illumination. The importance of the former factor is recognized by a 
comparison between the lowlands and uplands of Ceylon, the latter having 
an aquatic flora in which the blue-green element is almost as casual as it is 
with us. The influence of the intense light is shown by the minor part 
played by the Cyanophyceae in the smaller waters, which are often more 
or less shaded by surrounding vegetation. 
Table to show the Average Composition of Tropical 
Freshwater and Subaerial Floras. 
"<a 
s *• 
|| 
£ -S 
1 5 
§ 
C'O-S 
No. of submerged 
forms in reduced 
. ^3 
Vi 
Reference to Flora. 
Total No. of 
Species. 
s; 
'S 
f. 
ll 
^ £ 
No. of submerge 
green forms in 1 
total. 
No. of subaerii 
green forms in 
total. 
Percentage of 
forms in reduce* 
>1 
£ p 
Percentage ofbh 
forms in subaeri 
De Wildeman (’00) . . 
123(0 
40 
SShT.ai) 
27 
23 
59 
41 
4i 1 
Dickie (’81) . . . . 
IOI 
7° (3) 
28 
3(T.i) 
18 
21 
44 
56 
88 
(excl. Diatoms). 
Gomont (’02) . . . ) 
West and West (’02 A) ) 
141 
56 
36 
1 (T. 1) 
6 
13 
66 
34 
93 
Lemmermann (’06) . . 
173 
57 
29 
28 
5i 
49 
— 
Mobius (’88) .... 
32 
23 ( 1 ) 
14 
1 1 
4 
1 4 
65 
35 
80 
Nordstedt (’78) . . . 
113 
69 
39 
30 
57 
43 
— 
Schmidle (’00 A) . . . 
1 US 
9 1 (0 
34 
57 
37 
63 
— 
Schmidle (’02 b) 2 . . 
57 
47 
10 
37 
21 
79 
_ 
Schmidle (’03 a) . . . 
157 
78 
49 
29 
63 
37 
— 
Turner (’92) .... 
622 
86 
64 
22 
74 
26 
— 
West (’04) 
132 
66 
25 
1 
40 
40 
60 
— 
West and West (’98) 
63 
43 
4 
4 (T. 2) 
3 
I 32 
19 
81 
88 
West and West (’97 a) . 
298 
159(6) 
76 
8 (T. 2) 
38 
1 37 
53 
47 
82 
West and West (’02 b) . 
394 
99 (*) 
58 
8 (T. 7) 
33 
67 
33 
— 
Zeller (’73) 
126 
120 (2) 
45 
12 (T. 9) 
33 
1 30 
48 
52 
7 [ 
I am not aware of any direct statement in the literature as to the 
dominance of Cyanophyceae in the freshwaters of the tropics, although 
I feel convinced that Ceylon cannot be exceptional in this respect. More- 
over a consideration of the few relatively complete floras that we possess 
distinctly points to this group being an important one in all parts of the 
1 The large number of subaerial green forms (even when the 21 Trentepohlias are excluded) is 
due to the enumeration of a considerable number of forms (belonging to Chroolepideae) found 
growing on leaves (cf. p. 243). 
2 A large number of the forms involved in this case are from hot springs. 
