50 
STUDIES OF BRITISH FRESHWATER ALG^. 
In conclusion, we may once more survey the reproductive processes 
in the pond as a whole. The two most prominent periods of reproduc- 
tion are that in which Melosira and that in which Spirogyra is the 
reproductive form ; of these the latter is far more striking, and 
constitutes a very definite feature in the annual cycle in a normal year. 
In both cases we have the formation of resting-spores preceding a 
period of very diminished occurrence of the form involved. Apart 
from these two cases,i however, all the reproductive processes in the 
pond are purely asexual and vegetative, and do not lead to the 
formation of resting stages. This period of asexual and vegetative 
reproduction is generally most noticeable in the late summer and in the 
autumn, when there is a general increase of the different forms present 
in the summer, following on the summer-period of relative inactivity.^ 
This reproductive phase was especially noticeable in 1905. The forma- 
tion of the winter resting-condition on the part of the Cladophora 
(cf. p. 4C) may perhaps be regarded as marking a fourth period. The 
rather uniform conditions of temperature, etc., in Abbot’s Pool are 
probably responsible for the limited number of genera forming resting- 
stages. 
2^.— EPIPHYTIC FORMS. 
There is such an abundance of epiphytic growth in Abbot’s Pool 
that a few general remarks about it may well be added. As a general 
rule it may be said that epiphytes, although present in considerable 
quantity all the year round, are at their maximum during the warmer 
months of the year, this being particularly obvious during the 
midsummer of 1905. The epiphytic growth consists largely of Diatoms 
( Synedra radians, Sm., Cocconeis Pediculus, Ehrenb., Rhoicosphenia 
cnrvata (Kiitz.), Grun., Achnanthes , Epithe7nia turgida (Ehrenb.), 
Kiitz., Gomphonema acuminatum, Ehrenb., etc.), but other forms 
(such as Aphanochcete, Protoderma, Characium, ColeochcEte scutata, 
and species of ChamcEsiphon) also occur. 
The principal hosts are Cladophora and the Phanerogamic aquatics, 
when present. At certain times of the year, as already stated, 
Cladophora is practically concealed by a dense growth of Cocconeis 
and Epithemia, and it is only during its vigorous period (late spring 
and early summer) that we find many branches, which are quite clear 
of epiphytes. Next to Cladophora, CEdogonium seems to be the best 
host ; we have found it bearing Synedi'a radians, Achnanthes, 
Gomphojtema, Characium, ChamcEsiphon, and AphanochcEte, but 
Cocco 7 ieis and Epithemia do not occur on it. Both of these last-named 
forms are such as are attached by a broad base, and it seems likely 
that the small width of the CE‘^^?^6)/^^^/7;^-filaments does not afford a 
1 Vcmcheria, being only occasionally represented, is here left out of 
consideration. 
- Spirogyi^a is probably also at this period increasing by purely vegetative 
means (cf. p. 39). 
