52 THE GEOLOGICAL HISTORY OF PLANTS. 



of these bodies, and induced me to suspect, with Prof. 

 Orton, that they might have belonged to some group of 

 aquatic plants lower than the Lycopods. 



Since the publication of my paper on Khizocarps in 

 the Palaeozoic period above referred to, I have received 

 two papers from Mr. Edward Wethered, F. G. S., in one 

 of which he describes spores of plants found in the lower 

 limestone shales of the Forest of Dean, and in the other 

 discusses more generally the structure and origin of Car- 

 boniferous coal-beds.* In both papers he refers to the 

 occurrence in these coals and shales of organisms essen- 

 tially similar to the Erian spores. 



In the "Bulletin of the Chicago Academy of Science," 

 January, 1884, Dr. Johnson and Mr. Thomas, in their 

 paper on the " Microscopic Organisms of the Boulder Clay 

 of Chicago and Vicinity," notice Sporangites Huronensis 

 as among these organisms, and have discovered them also 

 in large numbers in the precipitate from Chicago city 

 water-supply. They refer them to the decomposition of 

 the Erian shales, of which boulders filled with these or- 

 ganisms are of frequent occurrence in the Chicago clays. 

 The Sporangites and their accompaniments in the boulder 

 clay are noticed in a paper by Dr. G. M. Dawson, in the 

 "Bulletin of the Chicago Academy," June, 1885. 



Prof. Clarke has also described, in the "American 

 Journal of Science" for April, 1885, the forms already 

 alluded to, and which he finds to consist of macrospores 

 enclosed in sporocarps. He compares these with my 

 Sporangites Huronensis and Protosalvinia bilolata, but 

 I think it is likely that one of them at least is a distinct 

 species. 



I may add that in the "Geological Magazine" for 

 1875, Mr. Newton, F. G. S., of the Geological Survey of 



* " Cotteswold Naturalists' Field Club," 1884; "Journal of the 

 Royal Microscopical Society," 1885. 



