Remarks on the Genera Callitriche and Elatine. 427 
between them is the shape of the leaves. Duby enumerates five 
varieties in France, four of which I have myself observed in Scot- 
land: 1. with the stem elongated and all the leaves obovate ; 2. with 
tlie lower leaves linear and the upper ones oval, which is the C. 
dubia, Thuil.; 3. with the stem very short and all the leaves oval, 
found in muddy ditches that are nearly dried up,—this is C. esti- 
valis, Thuil.; and 4. with all the leaves linear. This last I have 
not yet observed in fruit, but it has not at all the appearance of the 
two following species. In all these varieties the upper leaves ap- 
pear to be three-nerved. 
2. C. pedunculata ; fructiferous peduncles more or less elongat- 
ed, without bracteas at the base; fruit regularly tetragonal, each 
portion obtusely carinate at the back. 
Has. Ditch at Amberley, Sussex, between the Castle and the 
Wild Brook. 
In this species the fruit is about the same size as in the last. The 
leaves in all Mr. Borrer’s specimens are single-nerved and linear, 
agreeing in this respect with what I have lately received from Sar- 
dinia. M. De Candolle, however, says that the upper leaves are 
oblong and three-nerved in his plants. 
__ 3. C. autumnalis; fructiferous peduncles very short, without 
bracteas ; fruit irregularly tetragonal, each portion broadly and 
acutely winged at the back. 
Has. Loch of Clunie, at the landing-place close to the Castle. 
Outlet of Llyn Maclog, Anglesea, (Mr. W. Wilson.) 
What Petiver’s plant is, found near London, I have no means of 
ascertaining. ‘This species is very easily distinguished when grow- 
ing: the leaves are all linear, of a dark green colour, while the fruit, 
which is double the size of that in the two other species, is of a 
very pale yellowish green tint. Like the last, it flowers and fruc- 
tifies below the surface of the water, but the dorsal wing, as broad 
as that part of the fruit which actually contains the seed, at once 
distinguishes it. 
Of this genus De Candolle describes the seeds ‘‘ cum carpello 
concreta,’ by which, I presume, he means to say that they are at 
all points closely attached to, and incorporated with the carpell. 
Richard (Dict. Class. III. p. 60.) states that the ovulum is attach- 
ed to the upper and inner part of the cell, while Mr. Brown, (if I 
rightly understand the note in Hooker’s Flora Scot. Part II. p. 258.) 
and certainly Mr. Lindley, make the seeds peltate. To understand 
the subject better, I may observe, that from the axils of the leaves 
of the plant proceeds a small peduncle, at the summit of which is 
placed a quadrangular depressed pistillum, with two long subulate 
and glandular stigmata. As the fruit proceeds towards maturity, 
the four angles of the short germen expand, upwards, at the back, 
and downwards, each into a somewhat reniform lobe, whose point 
of attachment to each other is scarcely larger than in the germen 
state, and therefore appears now situated in the centre of the inner 
side of the lobe: each portion of the fruit may thus be called pel- 
