90 COMPOUND ORGANS OF PLANTS. 



herbaceous plants, growing in moist places, with stems about 

 half an inch in diameter and two feet high, which is increased 

 to a maximum of twelve feet in equinoctial marshes, and are 

 remarkable for the quantity of silex which enters into their 

 composition. The equisetiim is well known under the name 

 of horse-tail. 



131. The cellular Cryptogamia are seldom met with in a 

 fossilized condition. One or two instances are mentioned of 

 mosses being found fossil in the upper and tertiary deposits 

 only; but there is a general paucity of plants of this cha- 

 racter, whilst on the other hand there is a decided preponder- 

 ance of ferns and of the higher orders of the cryptogamia. 



132. Fossil Equisetaoese abound in the coal-measures and in 

 strata far more ancient; indeed, they appear to belong to the 

 earliest terrestrial flora of which any traces remain. Some of 

 them attained an enormous size, being from one to three feet 

 in diameter, and from thirty to forty feet high. In most in- 

 stances when these plants are found, their stems are pressed 

 flat, but specimens have been met with in a vertical position, 

 and retaining their cylindrical character. 



138. Fossil Ferns seldom exhibit any traces of fructification, 

 and are chiefly distinguished by the shape and forked venation 

 of their fronds. About one hundred and fifty species of fossil 

 ferns have been detected in the carboniferous strata in Eng- 

 land alone. The originals of many of these species were un- 

 doubtedly arborescent. Fossil fern-stems are rarely found, 

 yet a few have been discovered bearing all those characteristic 

 marks by which the tropical arborescent fern-stems are dis- 

 tinguished. Oicatriees, or soars, are left by the fiillen fronds 



