272 HISTORY OF BRITISH TERNS. 



placed rather nearer the inner margin ; the central cavity 

 is also proportionally smaller. It has, consequently, on 

 the exterior, a series of ridges formed of twin projections 

 representing the double row of siliceous particles which 

 extends along each ridge ; and a series of cavities rather 

 nearer the inner than the exterior surface of the ring. 



The fructification consists of small black cone-like 

 heads, of an oblong form, terminating in an apiculus. In 

 our specimens they appear sessile in the upper sheath, but 

 they are said to become elevated on a short pedicel. The 

 scales in one of these cones number about thirty. 



Equisetum ramosum is found on the moist banks of the 

 mountain glens of Scotland and the north of Ireland. It 

 was first found in Ireland, and apparently by two botanists 

 in company, Dr. Mackay and Mr. Whitla ; this was in 

 1833. It has subsequently been met with in other parts 

 of Ireland, as well as in Scotland. 



Equisetum hyemale, Linnceus. 



The Great Bough Horsetail. (Plate XX. fig. 1.) 



The underground stems of this plant are branched, and 

 creep to a considerable extent ; they are black, and fur- 

 nished with whorls of branched, black, fibrous roots. The 



