vii] THE HORNWORT 87 



of water plants in not excreting any slime, and their special 

 function if they possess one remains a mystery. 



It is characteristic of the Hornwort to occur sometimes in 

 such great abundance that it drives out nearly all other com- 

 petitors. It has been described, in the case of a certain Scottish 

 loch, as so luxuriant that a boat could only be rowed through 

 it with difficulty 1 . The present writer has seen it at Roslyn Pits, 

 near Ely, at the beginning of October, in such quantity that the 

 effect, on looking down into the water, was that of gazing into 

 a pure forest ofCeratophyllum. The axis at this season of the year 



FIG. 56. Ceratophyllum demersum, L. Vascular cylinder of stem in T.S. Small 



xylem space in the centre; xylem parenchyma thickened; phloem zone well 



developed with large sieve tubes, (x 130.) [Schenck, H. (1886).] 



is extremely brittle, snapping asunder at the slightest touch 

 and thus giving rise to countless detached fragments capable 

 of reproducing the plant. The apical regions of the shoots are 

 more crowded with leaves and more deeply green than the rest 

 of the plant, but are scarcely specialised enough to be called 

 winter-buds 2 . During the cold season the stems remain at the 



1 West, G. (1910). 



2 The existence of these winter shoots was noted by Royer, C. (1881- 

 1883); that the plant may vegetate throughout the winter was recorded 

 by Irmisch, T. (1853). 



