128 



THE GEOLOGICAL HISTORY OF PLANTS. 



menophyllacem, and the Marattiacece, go back to the coal- 

 formation.* 



Some of these ferns have the more complex kind of 

 spore-case, with a jointed, elastic ring. It is to be ob- 



FiG. 54. — Sphenoptens latior, Dawson. Coal-formation, a, Pinnule 

 magnified, with traces of fructification. 



serTed, however, that those forms which have a simple 

 spore-case, either netted or membranous, and without 

 annulus, are most common in the Devonian and lowest 



Fio. 65. — Fructification of Palseozoio ferns, a, Thecse of Arehceopterit 

 (Erian). i, Theca of Senftenbergia (Carboniferous), c, Thecae of 

 Asterotheca (Carboniferous). 



Carboniferous. Some of the forms in these old rocks are 

 somewhat diflBcult to place in the system. Of these, the 



* Mr. R. Kidston has recently described very interesting forms of 

 fern fructification from the coal-formation of Great Britain, and much 

 has been done by European palseobotanists, and also by Lesqugreux and 

 Fontaine in America. 



