124 ENGLISH BOTANY. 
rare in the north, but extending to Forfarshire. Rare, but widely 
distributed in Ireland. 
England, Scotland, Ireland. Perennial. Late Summer, Autumn. 
Stems wholly submerged, branched 1 to 3 feet long, densely clothed 
with whorled spreading leaves. Leaves 8 in a whorl, repeatedly forked, 
with the segments slender, rough at the edges. Fruit, which is rarely 
seen, about 4 inch long, ovoid, with 2 subulate spines at the base, and 
a longer curved one at the apex. Plant dark lurid green, rigid. 
Common Hornwort. 
French, Cornifle submergé. German, Rawher Igellock. 
Sus-Srecies I.—Ceratophyllum submersum. Linn, 
Prats MCCLXXVIL. 
Billot, Fl. Gall. et Germ. Exsice. No. 1992. 
Fruit when ripe covered with cylindrical tubercles, destitute of 
spines at the base, and tipped with a curved subulate style. 
In ponds and ditches in the south and east of England. Rare. 
England. Perennial. Late Summer, Autumn. 
Very similar to C. demersum, but with the segments of the leaves 
narrower and not serrulate; the fruit without spines or tubercles 
at the base, and, when mature (which I have seen only from St. Osyth, 
Essex), clothed with cylindrical tubercles, but smooth when young. 
There is certainly no constant difference in the foliage accompanying 
the absence of lateral spines in the fruit, and as this is rarely produced, 
it is impossible to say to which subspecies the greater number of 
British specimens belong. The fruit of all the Ceratophylla need 
never be looked for in deep water where the plants grow luxuriously. 
Besides these two subspecies there are two others found on the 
Continent, which are likely to occur in Britain; viz. C. platyacanthum, 
Chamisso, differing from C. demersum in the spines at the base of the 
fruit being compressed and winged at the bottom, and C. apiculatum, 
Chamisso, differing from C. submersum only in having 2 tubercles 
at the base of the fruit: these tubercles are evidently the rudiments 
of the spines of C. demersum, and consequently connecting the two 
supposed subspecies. 
Unarmed Hornwort. 
German, Glatter Igellock. 
