Reproduction of British Freshwater Algae in Nature. 433 
autumn or even in midwinter, 1 is undoubted, and it is quite possible that 
in some regions owing to certain climatic combinations such phenomena 
are more abundant than we have found them to be. If reproduction in 
Spirogyra is a result of intensification of certain factors, it is comprehensible 
that such intensification may occasionally occur at other times of the year 
than in spring, and that we may consequently find a species reproducing in 
the autumn or winter. 
We may briefly consider the one exceptional case we have observed ; 
this was in a pond at Telscombe, near Newhaven, in which 5 . cataeniformis 
(Hass.), Kiitz., and S. affijiis (Hass.), Petit, 2 were found reproducing 
abundantly from September to November, 1904. The following data as 
to the nature of the weather at this time of the year are taken from 
Brighton, 3 which is sufficiently near to Telscombe to justify the assumption 
that there were no marked differences. August and September, 1904, had 
a good deal more bright sunshine than is their wont (August had 249-36 
hours, while the average for the last twenty-seven years was 205-66 hours ; 
September had 192-50 hours, the average for the last twenty-seven years 
being 163-35). The mean temperature for September, 1904, was 58-1° F., 
which is about the average (58-4° F.) ; the extreme temperatures for this 
month were, however, much less than the average, the range being 44-1° F. 
to 70-6° F. (as against 35*9° F. to 83-2° F. for the last twenty-seven years). 
The rainfall was as follows: — July, 1904 = 0-52 in. (average 3-33 in.) ; 
August, 1904 = 1-71 in. (average 2-44 in.); September, 1904 = 1-64 in. 
(average 2-39 in.) ; October, 1904 = 2-47 in. (average 3-87 in.). The rainfall 
was therefore considerably below the average. August and September, 
1904, were certainly abnormal months meteorologically, and hence possibly 
the abnormal reproduction of the two species of Spirogyra. The very con- 
siderably larger number of hours of bright sunshine was probably one of 
the most important factors. 
D. Points of Systematic Interest. 
The determination of species of Spirogyra, even in the reproductive 
condition, is combined with so many difficulties that we have thought it 
best to figure a number of the species examined, so as to leave a permanent 
record. The following systematic details may also be of some interest. 
S. ternata , Ripart, is now usually regarded as a variety of S', neglecta 
(Hass.), Kiitz., 4 and our observations certainly support this view. In a pond 
in Sydenham Wells Park (July 2, 1906) filaments answering to Petit’s 
1 Cf. \V. and G. S. West, loc. cit., p. 33. 
2 Cf. Fritsch, Problems in Aquatic Biology, &c., loc. cit., pp. 164-7. The two species are 
here referred to as * S. gracilis .’ Renewed investigation of the sample has shown that this 
determination was incorrect. 
3 Cf. Brighton and Hove Nat. Hist, and Phil. Soc. Annual Report for 1905. 
4 Cf. also Petit, loc. cit., p. 27. 
