1895.] 



MICROSCOPICAL JOURNAL. 



25 



The attention of Sir J. W. Dawson was first directed 

 to these organisms, the Rhizocarps, by the late Sir W. 

 E. Logan in 1869. He obtained from the Brian shales 

 the Devonian of Kettle point, Lake Huron, specimens, 

 tilled with minute circular discs, to which he referred 

 in his report of 1863, as 

 "microscopic orbicular /i?:v ; 

 bodies." It was in a pa- 

 per published by Sir J. 

 W. Dawson in 1871, on 

 'spore cases in coal' that 

 he first described the fos- 

 sil remains in the slides 

 which was intercallated 

 with coal. These were 

 the same from the Erian 

 formation at Kettle Point 

 on Lake Huron, supposed to be on the horizon of the 

 Marcellus shale in New York. The Marcellus shale 

 is in the middle of the Devonian before the Carbonif- 

 erous coal came. 

 These remains are 

 the minute brown- 

 ish discs referred to. 

 They were recog- 

 nized as probably 

 spore cases or mac- 

 rospores of some ac- 

 rogenous plants. 



Acrogenous is ap- 

 plied to those cryp- 

 togamic or flower- 

 less plants, which increase by growth at the summit, or 

 " growing-point," as the tree-ferns. The shales also 

 contained immense numbers of granules, which most 

 likely may be the escaped spores, seeds or macrospores. 



