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Cn. XLVIII.] 



IN SUBAQUEOUS STRATA. 



5G7 



a quadrangular form (</). In Chara liispida^ whicli abounds 

 in a living state in the lakes of Forfarshire, and which has 

 become fossil in the Balde Loch, each of the spiral valves of 

 the seed-vessel turns rather more than twice round the circum- 

 ference, the whole together making between ten and eleven 

 rings. The number of these rings differs greatly in different 

 species, but in the same appears to be very constant. 



The stems of Charse occur fossil in the Scotch marl in 

 crreat abundance. In some species, as in Chara liisjpida^ the 

 plant when living contains so much carbonate of lime in its 

 vegetable organisation, independently of calcareous in- 

 crustation, that it effervesces strongly with acids when dry. 



Fig. 141. 



Stem and branches of Chara hispida, 



a. Stem and branches of the natural size. 



fc. Section of the stem magnified. 



c. Showing the central tube surrounded by two rings of smaller tubes. 



The longitudinal strise on the stems of Chara his^pida have 

 a tendency to be spiral, and as appears to be the case with 



worm 



from 



round in a contrary direction. 



stem 



com 



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