AZOLLA FI LICU LO IDES LAM. 
741 
definitely known about its introduction to Norfolk, where it was 
first noticed by F. H. Barclay in 1908 4 . There is evidence to 
show 5 that specimens were sent to Norwich in 1903 as “an 
interesting plant suitable for a pool in rock garden.” They 
w'ere grown in a greenhouse for a year or more and then 
placed in a pond in Chapel Field gardens, from wdiich 
they disappeared, but as the Yare valley is not concerned, 
there is no reason to doubt that these plants perished. It 
showed no tendency to spread beyond the limits of the one 
ditch at Woodbastwick until 1912, when a phenomenal rainfall 
flooded the low-lying districts in August, and then, in its optimum 
condition, with spores just reaching maturity, it was distributed 
broadcast. In January, 1913, it was seen in Woodbastwick 
Broad, in the river Bure at Salhouse, and in a dyke at Horning 
north of the river, and by July the summer growth covered 
large areas in Ranworth, South Walsham, and Cockshoot 
Broads. Following very high spring tides on the coast in 
September, with a consequent heaping up of water in the 
broads, the ebbs carried large mats of Azolla into the river, 
where they became familiar objects to the marshmen. East- 
ward it was traced as far as Stokesby, being specially noted, 
trapped in sheltered places at Horning Hall Dyke, Ant Mouth, 
Acle Boat Dyke, and Acle Bridge, where also it had got 
through the sluices into small drains. It was reported from 
St. Benet’s Abbey in August by Miss E. L. Turner, and near 
the bridge at Potter Heigham in October by Miss A. M. 
Geldart. 
The economic aspect of this alien water weed is already 
claiming consideration from river authorities and others 
interested in navigation, drainage, fisheries, etc. Being a free 
floating plant readily driven by wind and tide, it will not 
accumulate in the main channels, but in sheltered places it 
seems likely to control other vegetation by restricting light. 
The attention of those who are interested in its possible effect 
on motor navigation is directed to the following paragraph in 
4 Traus. Vol. VIII., p. 856. 
5 E. Peake in lit 1. xi. 13. 
