VII] CHAEA. 225 



walls of the fruit-case. The cells of the corona and stalk do not 

 become calcareous. In the fossil Charas, it is this calcareous 

 shell that is preserved. In the members of the Chareae the 

 stems are usually encrusted with carbonate of lime, and thus 

 have a much better chance of preservation than the slightly 

 calcareous Nitelleae. 



Chara. 



The generic characters have already been described in the 

 brief account of the family Chareae. 



The generic name was proposed by Vaillant in 1719S and 

 adopted by Linnaeus, who classed the Stoneworts with aquatic 

 phanerogams. As long ago as 1623" a figure of Chara was 

 published by Caspar Bauhin as a form of Equisetum. The 

 generic name Chara has usually been applied to recent and 

 fossil species alike. The existing species have a wide dis- 

 tribution ; Chara foetida, A. Br., a common British form, occurs 

 in practically all parts of the world. Stems and calcareous 

 'fruit-cases' oc'cur fairly commonly in a fossil state, and differ 

 but little from recent species, at least as regards essential 

 features. 



It is difficult to say at what geological horizon the Stone- 

 worts are first represented. The first certain traces of Chara 

 occur in Jurassic rocks, but certain spirally marked subspherical 

 bodies have been recorded from Devonian and Carboniferous 

 strata, which closely resemble Chara oogonia, and may be 

 Palaeozoic representatives of the genus. 



In 1889 Mr Knowlton^ of the American Geological Survey 

 described some 'problematic organisms' found in Devonian 

 rocks at the falls of the Ohio. Examples of these fossils are 

 shown in fig. 46 h and c; the spirally grooved body measures 

 from 1'50 to 1"80 mm. in diameter, and about 170 mm. in 

 length. The Chara-like character of the fossils had been 

 previously suggested by Meek^ in 1873. Without going into 

 the arguments for or against placing these fossils in the Chareae, 



1 Vaillant (1719) p. 17. » Migula (90) p. 53. 



8 Knowlton (89^). * Meek (73) p. 219. 



15 



