FRESH-WATER ALG. 233 
were transmitted for examination to Ehrenberg, 
who found the colouring matter to consist of ex- 
tremely minute alge, or animalcules as he called 
them, somewhat allied to the Palmella prodigiosa. 
A similar appearance was observed on bread in 
Philadelphia in 1832 when the cholera was pre- 
vailing in that city. In the spring of the year 
1825, the waters of the Lake of Morat presented 
an appearance in many places of being coloured 
with blood, and popular attention was speedily 
directed to this strange occurrence. M. de 
Candolle, however, proved that the phenomenon 
in question was caused by the development of 
myriads of the purple conferva (Oscéllatoria 
vubescens). The phenomenon occurred every 
spring for several years, when the fishermen of 
the neighbourhood, more poetical than this class 
of persons usually are, remarked that ‘the lake 
was in flower’ M. Montagne records a similar 
phenomenon in the Comptes Rendus. He hap- 
pened to be at the Chateau du Parquet in July 
1852, when the temperature had been exceedingly 
high for about ten successive days. This con- 
tinued warmth of the atmosphere was probably 
instrumental in providing the conditions suitable 
for the development of a red parasite, which 
attacked all kinds of alimentary substances, and 
particularly pastry, imparting to them a bright 
