LONDON BOTANICAL EXCHANGE CLUB. 71 
Allium oleraceum, L. From Plymouth ; collected by Mr. Briggs. 
Additional to the list of Devon species. 
Wolffia arrkiza, Wimm. (Lemna, Linn.). Mr. Syme sends a plen- 
tiful supply of this recent addition to our flora from Staines, Middle- 
sex. This pond and one at Walthamstow, Essex, are the only stations 
hitherto discovered in England for this little plant. 
Potamogeton decipiens, Nolte. For the addition of this species to 
the British flora we are indebted to Mrs. Hopkins, of Bath, who has 
for several years recognized it as distinct, and now sends a supply of 
specimens (which unfortunately did not reach us before the parcels 
were sent out) from a canal in the neighbourhood of that city. From 
these the following description is taken : — Stem long, terete, copiously 
branched. Leaves uniform, all submerged, membranous, bright grass- 
green, sessile, oblong, 2-3 inches long, 1-1£ inch broad, the edge not 
thickened or denticulate, the apex blunt with a slight mucro, the base 
also rounded ; the midrib flattened with 3-6 fine longitudinal veins on 
each side of it, connected by fine regular transverse veinlets. Stipules 
j-4 inch long, not winged on the back. Peduncle considerably 
thicker than the stem, under 2 inches long, about equal in thickness 
throughout. Spike more than 1 inch long when fully developed. 
Lamina of the sepals nearly round. The plant comes very near to 
■P. lr<ce?/s, but in that the leaves are not so much rounded at each end, 
slightly stalked, and the border is thickened and minutely denticulate ; 
the stipule is winged on the back on the lower part, and the peduncle 
is mcrassated upwards. P. prcelomui has leaves with a similar border 
to those of P. decipiens, but they are different in shape, much more 
lengthened out and hooded at the apex, and the peduncle is more 
slender and three or four times as long. P. decipiens is admirably 
figured in Reichenbach's * Icones,' vol. vii. t. 35 ; and dried specimens 
have been issued in Reichenbach's Fl. Germ. Exsic. n. 1603, and the 
Herbarium Normale' of Fries. We have seen specimens also from 
Upsala, gathered by Dr. Andersson, and from Geneva, gathered by 
D*. Lagger. Descriptions will be found in Reich. Ic. Fl. Germ., vol. 
vu - p. 22, and Koch's Syn. Fl. Germ., p. 779. None of the speci- 
mens we have examined have been in fruit, but, according to Hartman, 
^ is similar to that of P. lucens (Skandinavens Flora, p. 214). In 
Northern Germany the plant has been gathered in Holstein, Schleswi 
and the vicinity of Hamburg, but it is not included in the French 
floras. 
