740 
AZOLLA FI LIC ULO IDES LAM. 
into Europe of late years. It is now reported from several 
localities in Britain, France, Germany, Holland and Italy. 
In the British Islands Azolla has been recorded for Berk- 
shire, Cambridgeshire, Cheshire, Devonshire, Essex, Gloucester- 
shire, Kent, Norfolk, Oxfordshire, Worcestershire and Ireland. 
In most of the stations the species is stated to be A. caroliniana 
Willd. I have had opportunities to examine specimens from 
the Cherwell near Oxford (F. Long) , the Pang near Sulham, 
and the Thames near Pangbourne (G. H. Adams) ; marsh 
ditches close to the coast between Sandwich and Pegwell (F. 
Newton) ; and Bristol (Prof. Priestley). All were the same 
as our Norfolk plant and must be referred to A. filiculoides 
Lam. A similar confusion of these two species has occurred in 
America. Campbell 3 says: — “Until very recently American 
botanists confounded A. filiculoides with A. caroliniana of 
Eastern America, and in the Botany of California only the latter 
species is mentioned. I have examined material from various 
parts of California, and in all cases the plants were undoubted 
specimens of A. filiculoides." 
A possible cause for this confusion is the difference in appear- 
ance between mature and immature plants. In the young state, 
when absence of spores makes identification difficult, the 
general tone of the massed plants is dull olive green with dull 
red marginal bands to the leaves. The plant is smaller, more 
compact, and lies flatter on the water because both dorsal and 
ventral lobes are closely imbricated. At maturity, when identi- 
fication by spore characters is easy and certain, the colour 
changes to a pale green with hyaline leaf margins, and the 
ventral lobes, which are strongly tinged with pink and undulated, 
stand out from the stem at a wide angle, giving the plant a 
different appearance and making it look much larger. At least 
one specimen that had been authoritatively named A. caroliniana 
proved to be immature A. filiculoides with closely adpressed 
leaves. Judging from material that has come to hand from 
widely-separated localities, it seems possible that all British 
records for A ■ caroliniana are based on this error. Nothing is 
3 Ibid. p. 155. 
