THE CARBONIFEROUS FLORA. 



119 



relation to our modern equisetnms, or mare's- tails, but, 

 as in other cases wo have met with, are of gigantic size 

 and comparatively complex structure. Their stems, in 

 cross-section, show radi- 

 ating bundles of fibres, 

 like those of exogenous 

 woods, yet the whole plan 

 of structure presents some 

 curious resemblances to 

 the stems of their hum- 

 ble successors, the mod- 

 ern mare's-tails. It would 

 seem, from the manner 

 in which dense brakes of 

 these Calamitcs have been 

 preserved in tlie coal-for- 

 mation of Nova Scotia, 

 that they spread over low 

 and occasionally inun- 

 dated flats, and formed 

 fringes on the seaward 

 sides of the great Sigilla- 

 ria forests. In this way 

 they no doubt contrib- 

 uted to prevent the invasion of the areas of coal ac- 

 cumulation by the muddy waters of inundations, and 

 thus, though they may not have furnished much of the 

 material of coal, they no doubt contributed to its ])urity. 

 Many beautiful plants of the genera AsterophylUtes and 

 Annularia are supposed to havo beeii allied to the '^.ah- 

 mitea, or to have connected t!inr.ii wiih tlio Rhizoar'ps. 

 The stems and fruit of these plants have strong points of 

 resemblance to those of SphenopJit/Ihtrn, and the leaves 

 are broad, and not narrow and angular like those of the 

 true Calamitcs (Fig. 45). 



No one has done more than my friend Dr. William- 



Fio. 42. — Erect Siiiillaria, ptai:din,gf 

 on a coal-soam (S. Jogj^ang^ Novu 

 Scotia). 



