Algal Flora of the Tropics. 
267 
25 . Oedogonium 
26. 
C. In the following 
1 . Oedogonium 
2. 
4 - 
5* 
6 . 
7- 
D. The diameter is 
1 . Oedogonium 
2. 
3* 
E. The diameter is 
1 . Oedogonium 
undulatum (Br6b.), A. Br., var. senegalense, Nordst. (14-20/*): — 
Nordstedt, ’80, p. 13. 
Welwiischii, W. and G. S. West (17-24/*) : — West and West, 
’97 a, p. 5. 
species the diameter is 30 /* or less : — 
cyathigerum , Wittr., f. ornatum (Nordst.), Hirn (21-30/*) : — 
Wittrock, ’ 78 , p. 134. 
cyathigerum , var. hormosporum (W. and G. S. West), Hirn 
(22-30/*): — West and West, ’97 a, p. 5 (sub O. hormo- 
sporum, W. and G. S. West ; in stagnis pr. Catumba) ; 
Schmidle, ’03 a, p. 86 (ditch near Langenburg). 
indicum , Hirn. (20-25/*): — Schmidle, ’00 a, p. 160 (no 
locality given). 
oboviforme, Wittr. (21-32 /*) : — Wittrock, ’78, p. 140. 
plagiostomum , Wittr., var. gracilius, Wittr. (22-25/*): — 
Wittrock, ’78, p. 142. 
spirale , Hirn, var. acutum , W. and G. S. West (22-25/*): — 
West and West, ’02 b, p. 128 (rice-fields). 
Wolleanum, Wittr. (21-30 /*): — Schmidle, ’00 a, p. 160 (no 
locality given), 
below 40 /* in : — - 
dioicum , Carter (31-35/*): — West and West, ’02 a , p. 159 
(stagnant water). 
Landsboroughi (Hass.), Wittr. (31-40/*): — Schmidle, ’00 a , 
p. 160 (no locality given); Zeller, '73, p. 188. 
mexicanum , Wittr. (34-40 /*) : — Wittrock, ’78, p. 138. 
over 40 /* in : — 
fabulosum , Hirn, var. maximum , W. and G. S. West 
(83-93/*): — West and West, ’02 a, p. 159 (sub O. 
maximum , W. and G. S. West ; stagnant water). 
Kurzii , Zeller (44-52 /*) : — Zeller, ’73, p. 189 (marsh). 
sub octangular e, W. and G. S. West (50-54 /*) : — West and 
West, ’02 b, p. 127 (rice-fields). 
The list shows the great prevalence of narrow forms ; by far the 
majority (viz. 51) are less than 20 n, and only thirteen species exceed these 
dimensions. I have above indicated that I am inclined to explain this as 
a result of the small amount of dissolved oxygen in the water. In all the 
forms whose filaments are more than 20 /x in width data as to habitat have 
been added, where these are available. These data, however, do not show 
that the broad forms in question are found in anything but stagnant water, 
so that it does not appear that they have got over the difficulties of poor 
aeration by frequenting special habitats. O. suboctangulare , to judge by the 
figures (West and West, *02 B, PI. XVII, Figs. 1, 2), has exceptionally 
thin walls, and the same is true to a less extent of O. fabulosum, var. 
U 
