APETAL^ 265 



heard of, much less seen, this interesting plant, or its 

 rarer ally C. suhmersum. 



The generic name applied by Linnaeus has reference 

 to the spiny or horn-like leaf-segments. 



Probably the Hornwort from the above reasons has 

 a wider distribution in the British Isles than is 

 generally supposed. It occurs generally in the 

 British Isles, but not in West Scotland or rarely, and 

 in Ireland it is rare. It is found in the Channel 

 Islands. 



Pools, ponds, ditches, slow streams, canals, back- 

 waters, shallow margins of lakes, form the habitat of 

 the Hornwort. It is a member of the fresh-water 

 aquatic formation, where it is found in waters 

 relatively rich in mineral salts, in nearly stagnant 

 waters, in the submerged-leaf association. 



Aquatic in habit, Hornwort forms dense masses, 

 usually at or near the bottom of the piece of water 

 in which it grows, but being rootless it does not 

 absolutely grow on the mud, but lies half-way up in 

 the water. Willis says that '* The plant decays 

 away behind as it grows in front (like Sphagnum) so 

 that vegetative multiplication occurs by the setting 

 free of the branches. The old leaves are translucent 

 and horny, whence the common name. Winter buds 

 are not formed, the plant merely sinking to the 

 bottom in autumn and rising again in spring." As 

 in other aquatic plants, the plant is smooth and has 

 no hairs. It is very leafy. The stem is slender and 

 brittle, breaking in the hand. The habit is much 



