378 THE JOURNAL OF GEOLOGY. 



to admit of their study under the microscope. The parts usu- 

 ally exhibiting internal structure are stems, branches, roots, and 

 other normally hard organs, yet in exceptional cases every part 

 of the plant, including the leaves, buds, and flowers, are so per- 

 fectly preserved that they may be as successfully studied as 

 though living. An example of this kind is afforded by the Car- 

 boniferous groups of Cordaites, found in a state of silicification 

 in central France. 



Plants that are so preserved as to retain their internal struc- 

 ture, admit of closer study and characterization than is usually 

 attained for other plant organs. So valuable is this method that 

 Professor W. C. Williamson, the distinguished English paleo- 

 botanist, was led to say^ "that no determinations respecting 

 fossil plants can have much absolute value save such as rest 

 upon internal organization ; that is the basis upon which all sci- 

 entific recent botany rests, and no mere external appearances can 

 outweigh the positive testimony of organization in fossil types." 

 Therefore, when it is possible to obtain plant remains with the 

 internal structure preserved, it may be safely set down that they 

 will afford valuable and reliable data for stratigraphic identifica- 

 tion. 



The study of the internal structure of fossil plants is yet 

 young in North America, and while a broad field remains for 

 future investigation, enough has alreadv been accomplished to 

 show its value. A few examples may be cited : 



In 1888, Araucarioxyloji Arizojiicum was described from the 

 Trias (Shinarump group of Powell) of New Mexico. The same 

 species has been found characteristic of the Trias of North 

 Carolina'' and of the copper mines near Abiquiu, New Mexico. ^ 



In his paper on the geology of Skunnemunk Mountain, 

 Orange county. New York,'* Professor C. S. Prosser relies upon 



' On the Organization of tlie Fossil Plants of the Coal Measures. Roy. Soc, Lon- 

 don. Phil. Trans.. Vol. 161; 187 1; p. 492. 

 ^Russell: The Newark System, p. 29. 



3 Fontaine and Knowlton : Notes on Triassic plants from New Mexico. Prcc. 

 U. S. Nat.' Mus., Vol. XIII., 1890, pp 281-285. 



4 Trans. N. Y. Academy Science, Vol. XL, June, 1892. 



