IJfTEODUOTION. 11 



Allen suggests that this may be protective in character, 



deterring animals from feeding on them. 



The Charophyta have been turned to 



Economic comparatively little use in the economic 

 uses. '^ '' 



world. Le Maout and Decaisne remark : 



*' This family is really useless to man," but they add ; 



" some species of Ghara are covered with calcareous 



salts, and are used for polishing plate, whence their 



common names of ' Herbe a ecurer ' and ' Lustre 



d'eau.' " * 



Large banks, formed of the remains of the decayed 

 plants, are frequently to be found in waters where 

 they grow freely, and deposits of so-called " Chara- 

 marl " occur in abundance in the alluvial formations of 

 the East Anglian and Irish fenlands,' varying from a 

 few inches to three feet or more in thickness. These 

 deposits are often termed " shell-marl," but this name 

 is misleading, since by far the greater part of their 

 substance is composed of Chara-debris. Neither these 

 deposits of the past, nor the decayed growth now 

 accumulating, have been utilized to any considerable 

 extent. Skertchley, in the ' Geological Survey Memoir 

 of parts of Cambridgeshire and Suffolk,' p. 198 (1891),. 

 states that in the fens between Burwell and Laken- 

 heath " the shell-marl is dug for manure and known 

 as chalk-marl." 



Messrs. Kennard and "Woodward quote Wesenburg- 

 Lund ('Medd. Dansk. Geol. Foren.,' No. 7, 1901), as 

 stating that at Hingeso in Jutland the Chara-marl " is 

 dug out of the lake by machinery and made use of for 

 agricultural purposes," f 



* 'Descriptive and Analytical Botany' (Translation), p. 921. 

 ■j- "The Post-Pliocene Non-Marine MoUusca of Ireland," by A. S. Kennard 

 and B. B. Woodward, in 'Proc. Geol. Assoc,,' xxviii, p. 155. 



