2 45 
Algal Flora of the Tropics. 
tropics. The table on the preceding page is an analysis of the data in a 
number of these floras with reference to this point. The numbers, of course, 
only refer to species ; there is no means of finding out the numbers of indi- 
viduals. This is unsatisfactory, but it does show certain points. Since the 
smaller unicellular and colonial forms are as a rule quite subsidiary to the 
larger ones, I have thought it well, in order to get a better idea of the 
systematic composition of a flora, not to include the Desmids, Diatoms, 
Peridineae or Flagellates in these calculations. 
In explanation of this table I have still to mention that the few fresh- 
water species of Florideae have been included amongst the green sub- 
merged forms in order to avoid undue complication ; where there are records 
of such forms the number of species is added in brackets after the reduced 
total (in the second column). Since the species of Trentepohlia are often 
a considerable increment in the green subaerial flora, their number has been 
indicated in brackets behind the actual total, in the fourth column (preceded 
by the letter T, which stands for Trentepohlia). In many cases the habitat- 
data were not sufficiently precise to enable one to distinguish between 
submerged and subaerial forms, so that the green and blue-green forms could 
only be included as a whole ; in these cases it was, of course, impossible to 
give a percentage in the last column. All marine forms have been excluded. 
The percentages are calculated to the nearest whole number. 
Before proceeding to discuss the features illustrated by this table, we 
will just take three European freshwater algal floras for comparison. For 
this purpose I have selected Messrs. W. & G. S. West’s Freshwater Algae 
of the South of England 1 ; Borgesen’s Freshwater Algae of the Faeroes 2 ; 
and Borge’s Beitrage zur Algenflora von Schweden 3 . They illustrate the 
flora of regions which are sufficiently far apart and diverse in all except the 
temperate climatic conditions, and so there can be no fear of our dealing 
with a local aspect of European algal vegetation. Any other algal flora 
from our parts would give practically the same results as these do. 
Table to show Average Composition of Freshwater Algal 
Growth in three European Floras. 
Flora . 
Total 
No. of 
Species. 
Total , less 
Desmids , 
Diatoms, 
Zfc. 
No. of green 
forms in re- 
duced total. 
No. of blue- 
green forms 
hi reduced 
total. 
Percentage of 
green forms 
in reduced 
total. 
Percentage of 
blue-green 
forms in re- 
duced total. 
W. and G. S. West 
588 
255 (2) 
*94 
61 
76 
24 
Borgesen .... 
323 
148 (1) 
107 
4 i 
72 
28 
Borge 
472 
191 (1) 
149 
42 
78 
22 
1 Journ. Roy. Microscop. Soc., 1897, p. 467 et seq. 
2 Botany of the Faeroes. Pt. I, Copenhagen, 1901, p. 198 et seq. 
3 Arkiv for Botanik, Bd. 6, No. 1, 1906. 
