124 ENGLISH BOTANY. 



rare in the north, but extending to Forfarshire. Rare, but widely 

 distributed in Ireknd. 



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 I 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, Gorniflo submerge. German, liaiiher hjellock. 



Sub.Species II.— Ceratophyllum submersum. Linn. 



Plate MCCLXXVII. 



Billot, Fl. Gall, et Germ. Exsicc. 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 m 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 Igelloch. 



