

ROOM I. 



EQUISETUM ANNULARIA. 



27 



the same plane with the stems whence they proceeded, and, 

 in consequence, their remains present a very elegant appear- 

 ance when expanded on the schist. 

 Each whorl is composed of from 

 twenty to thirty linear lanceolate 

 leaves, which are united at their 

 base, so as to form a zone around 

 the stem: it is supposed that they 

 were aquatic, or marsh plants, the 

 stems and leaves floating on the 

 surface of the water. 1 Both these 

 extinct types of plants are common 

 in the carboniferous strata. 2 



1 2 3 



LIGN. 3. EQTTISETUM LYELLII. POUNCEFOKD. 

 Fig. 1. Stem \vith two sheaths, and a head at the lowermost joint. 



2. Stem of a young plant, pyritified. 



3. Stem with the cryptogamous head. (Nat. size.) 



EQUISETACE^;. Case A. Fossil plants allied to the Equi- 

 setum (Mare's-tail). The family of the Equisetacese comprises 



1 See " Tableau des Genres de Yggetaux Fossiles." Par M. Adolphe 

 Brongniart. Paris, 1849. 



2 Plate V. of "Pictorial Atlas of Organic Remains" contains coloured 

 figures of both genera. 



