PLANTS OF THE COAL. 



201 



rays of the noon-day sun. Soil is to them a something to keep 

 them stationary, rather than a source of nutriment, which in 

 these plants is conveyed by 

 myriads of small cuticular pores 

 to the cellular tissue which lies 

 beneath them. The accompany- 

 ing is a figure of a typical spe- 

 cies of this family (fig. 139). 



III. CALAMITES. These 

 have already been described as 

 allied to the equisetacece, or 

 horse-tail tribe ; but they differ 

 in their much larger size, the 

 analogous plants in these re- 

 gions being only two feet high, 

 while a gigantic species of the 

 tropics is no more than five feet 

 in height, and an inch in dia- 

 meter ; whereas their fossil re- 

 presentatives far exceed these 

 dimensions, both in circumfe- 

 rence and elevation ; they were 

 farther distinguished by having 

 a thin bark, and are now gene- 

 rally considered a separate and extinct family.* 



IV. THE CONIFEEJB. It has been observed, as a remark- 

 able circumstance, that the fossil conifers of the coal 

 bear a close resemblance to 



those of the existing genus 

 araucaria, or Norfolk Island 

 pine; slices of the wood, when 

 examined by the microscope, 

 showing that the ducts or 

 glands peculiar to this family 

 are arranged in a similar 

 manner ; that is, alternately 

 in double and triple rows 

 (fig. 140). 



V. SiiGMAEi-ZE. These 

 have recently been most 



Fio. 139. Crassula tetragona, from 

 De Candolle's Plantes Grasses. 



FIO.UO. 



ully and ably described by 



* Plot. Atlas, pi. xv., xvl, xvii. 



