66 
E. Marion Delf. 
occasionally and sparsely, whilst others, such as Tetraspora and 
Volvox, appear occasionally but in considerable amount. This 
spasmodic appearance of one form in abundance is usually limited 
to a small region of a single pond, so that the causes must be very 
local as well as of a temporary nature, {n the following table of 
the algae which have been observed in the whole series of ponds the 
figures give the number of occurrences noted between January, 
1912 and March, 1914, irrespective of the amount observed in any 
sample: they thus express to some extent, the frequency of any 
particular form in the ponds. 
FLAGELLATA. 
Synura uvella ... ... 60 
Peridinium sp. ... ... 56 
Euglena... ... 21 
Dinobryon sertularia ... 17 
Ascoglena ... ... 16 
ULOTRICHALES. 
1 Ulothrix subtilis ... 49 
1 Microspora floccosa ... 33 
Draparnaldia ) 9 ponds, 
glomerata i 25 cascades 
Chaetophora risiformis 16 
Stigeoclonium. 1 
PROTOCOCCALES. 
Aphanochaete repens ... 
3 
Chlamydomonas sp. 
48 
Coleochaete scutata 
4 
... 
Carteria ... 
... 
11 
STEPHANOKONT^E. 
Phacotus 
7 
CEdogonium (2 sp.) 
Gonium lacustre 
24 
33 
Pandorina 
... 
14 
„ ciliatum ... 
1 
Eudorina 
... 
3 
HETEROKONT^E. 
Volvox ... 
... - 
9 
1 Tribonema affinis 
86 
Tetraspora 
... 
18 
1 „ bombycina ] 
Palmodictyon ... 
... 
8 
Vaucheria sessilis ...i 
Palmellococcus... 
... 
6 
„ geminata ...1 
4 
Selenastrum 
... 
3 
Mischococcus ... 
3 
Scenedesmus ... 
• • • 
12 
Characium 
• • • 
7 
AKONTyE. 
Chlorochytrium... 
• • • 
1 
1 Spirogyra beilis 
Sphaerocystis ... 
... 
20 
1 „ decimina ... 
Trochiscia 
• •• 
1 
1 „ nitida 
- 106 
Tetraedon 
... 
* 1 
1 „ gracilis 
Chaetosphaeridium 
3 
„ sp. ? 
i 
Stipitococcus ... 
... 
1 
1 Mougeotia scalaris ...i 
81 
Dictyosphaerium 
• . • 
2 
„ parvula? ...j 
1 I am indebted to 
Professor G. 
S. West for the identification of these 
species. 
