98 CRITIQUES AND ADDRESSES. [r. 



But this explanation is at once shown to be untenable 

 when the smaller and the larger sacs are proved to be 

 spores or sporangia. 



Some, once more, have imagined that coal was of sub- 

 marine origin ; and though the notion is amply and easily 

 refuted by other considerations, it may be worth while 

 to remark, that it is impossible to comprehend how a 

 mass of light and resinous spores should have reached 

 the bottom of the sea, or should have stopped in that 

 position if they had got there. 



At the same time, it is proper to remark that I do 

 not presume to suggest that all coal must needs have 

 the same structure ; or that there may not be coals in 

 which the proportions of wood and spores, or spore-cases, 

 are very different from those which I have examined. 

 All I repeat is, that none of the coals which have come 

 under my notice have enabled me to observe such a dif- 

 ference. But, according to Principal Dawson, who has 

 so sedulously examined the fossil remains of plants in 

 North America, it is otherwise with the vast accumula- 

 tions of coal in that country. 



"The true coal," says Dr. Dawson, "consists principally of the 

 flattened bark of Sigillarioid and other trees, intermixed with leaves of 

 Ferns and Cordaites, and other herbaceous debris, and with fragments 

 of decayed wood, constituting ' mineral charcoal,' all these materials 

 having manifestly alike grown and accumulated where we find them." l 



When I had the pleasure of seeing Principal Dawson in 

 London last summer, I showed him my sections of coal, 

 and begged him to re-examine some of the American 

 coals on his return to Canada, with an eye to the presence 

 of spores and sporangia, such as I was able to show him 

 in our English and Scotch coals. He has been good 

 enough to do so ; and in a letter dated September 26th, 

 1870, he informs me that 



1 " Acadian Geology," 2nd edition, p. 138. 



