AZOLLA FILICULOIDES LAM. 
739 
The following conclusions were drawn from the observed 
facts : — 
A moderately warm temperature is needed to induce germi- 
nation. Development in a cold house in May — the mean shade 
temperature in Norwich being 52° F., with a maximum 
exceeding 80° F. — may be compared with germination in 
sixteen days in midwinter at a temperature of 60° F. (40° — 70° 
range). 
Germination requires certain conditions of illumination and 
aeration. Spores which accumulate year after year and would 
finally perish if left in the rather deep, stagnant, heavily-shaded 
ditch at Woodbastwick, germinate on exposure to light, perhaps 
more readily after exposure to air. This consideration has a 
local interest, for sexual regeneration is likely to be more 
general in the varied conditions offered by the extensive 
waterways to which the plant has now gained access. Its 
rampant growth in 1912-13, in contrast with previous isolation 
for several years in a single ditch, is significant. The large 
proportion of immature plants on Ranworth Broad and 
elsewhere showed that the spores distributed by the August 
flood of 1912 had played a great part in the inoculation of 
Broadland. 
The genus Azolla, though not indigenous to Europe nor to 
North-West Asia, is widely distributed in both hemispheres. 
A. filiculoides Lam. and A. caroliniana Willd. are American 
species, the former extending over eighty degrees on the west, 
from Patagonia northwards to California ; the latter being 
restricted to the east, from Brazil northwards to Lake Ontario. 
In Australia, New Zealand and New Holland, A. filiculoides 
var. rubra Bak. is found. A. pinnata R. Br. occurs in South 
and West Africa, Japan, Ceylon, and several East Indian 
Islands. A. nilotica De Caisne is restricted to the White Nile 
and adjacent waters. 
Azolla has been introduced to Europe during the last forty 
years. In 1873, Strasburger had no living material available. 
In 1892, Belajeff stated that A filiculoides had been introduced 
