Studies on the Occurrence and Reproduction of British 
Freshwater Algae in Nature. 
I. Preliminary Observations on Spirogyra. 
BY 
F. E. FRITSCH, D.Sc., Ph.D., F.L.S., 
Assistant Professor of Botany, University of London, University College , 
AND 
FLORENCE RICH, M.A. 
With Eleven Figures in the Text. 
A. Introductory. 
I N the course of extensive investigation of periodical samples of Algae 
from various ponds, situated mainly in the south of England, a con- 
siderable number of facts regarding the occurrence and reproduction of 
Spirogyra have come to light. Certain data dealing with the biology 
of this genus have already been published , 1 but we believe that the subject 
has not yet been approached from exactly the same point of view as that 
adopted in the present paper. A general preliminary account of the results 
so far obtained may thus be of some value. It is proposed in subsequent 
papers of this series to deal with other genera of freshwater Algae in 
the same way. 
The materials on which our observations are based have been collected 
by the method already described in some detail by one of us , 2 and it 
1 See especially Messrs. W, and G. S. West, Observations on the Conjugatae. Annals of Botany, 
vol. xii, No. xlv, 1898, p. 29 et seq. J. Comere, Observations sur la periodicite du developpement 
de la flore algologique dans la region toulousaine. Bull. Soc. Bot. de France, t. liii, 1906, p. 390 et 
seq. G. Klebs, Die Bedingungen der Fortpflanzung bei einigen Algen und Pilzen. Jena, 1896, 
p. 229 et seq. 
2 Cf. Fritsch, Problems in Aquatic Biology, &c. New Phytologist, vol. v, No. 7, 1906, 
p. 149 et seq. 
, [Annals of Botany, Vol. XXI. No. LXXXIIL July, 1907.] 
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