36 



THE GEOLOGICAL HISTORY OF PLANTS. 



kind from the coal-formation of Nova Scotia, which is 

 described in "Acadian Geology" * (Fig. 12). 



I have referred to these facts here because they are 

 relatively more important in that older period, which may 

 be named the age of Algae, and because their settlement 

 now will enable us to dispense with discussions of this 

 kind further on. The able memoirs of Nathorst and 

 Williamson should be studied by those who desire further 

 information. 



But it may be asked, "Are there no real examples of 

 fossil Algae ? " I believe there are many such, but the diffi- 

 culty is to distinguish 

 them. Confining our- 

 selves to the older 

 rocks, the following 

 may be noted : 



The genus Bu- 

 tliotrcphis of Hall, 

 which is characterised 

 as having stems, sub- 

 cylindric or com- 

 pressed, with numer- 

 ous branches, which 

 are divaricating and 

 sometimes leaf -like, 



contains some true Algae. Hall's B. gracilis, from the 

 Siluro-Cambrian, is one of these. Similar plants, referred 

 to the same species, occur in the Clinton and Niagara 

 formations, and a beautiful species, collected by Col. 

 Grant, of Hamilton, and now in the McGill College col- 

 lection, represents a broader and more frondose type of 

 distinctly carbonaceous character. It may be described 

 as follows : 



Buthotrepliis Grantii, S. N. (Fig. 13). Stems and 



FIG. 12. Cone-in-cone concretion (Carbon- 

 iferous, Nova Scotia), illustrating pre- 

 tended Algae. 



* Appendix, p. 676, edition of 1878. 



