398 



On the Fossil Plants of the Coal-measures. [June 19, 



finds the peculiar triangular fibro-vascular bundle so characteristic o£ 

 Asterophyllites ; and in all remains of the same trifid origin of the 

 vascular layers may be traced in the peculiar curvatures assumed by the 

 vascular laminsB as they proceed from within outwards. The bark 

 consists of two layers : the inner one is composed of ordinary paren- 

 chymatous cells, often of considerable size ; the outer one consists of 

 irregular piles or columns of cells, disposed perpendicularly to the 

 surface of the bark, and with their tangential septa in close contact and 

 in parallel planes. The lateral or radial boundaries of these piles of 

 cells are more strongly denned than the transverse septa. In tan- 

 gential sections of this outer bark, each of these radially disposed columns 

 of parallel-sided cells appears as a single thick-walled parenchymatous 

 cell, whose aspect, in common with that of its neighbours, is that of 

 ordinary coarse parenchyma. Such sections exhibit no indication of the 

 radial elongation of these cells seen in radial and transverse ones. On 

 reexamining the inner bark, we discover the explanation of these ap- 

 pearances. Many of the larger and more peripheral of the cells of the 

 latter are seen to be undergoing division by the development within their 

 walls of secondary cell- partitions, which are parallel with those of the 

 radially disposed columns. It appears obvious that each of the latter 

 was primarily one of the cells of the inner bark, which has become elon- 

 gated radially, and at the same time divided into a linear series of com- 

 pressed cells by the growth of a succession of secondary divisions, all of 

 which were more or less tangential to the periphery of the stem. 



The author directs special attention to the genetic activity of this inner 

 bark ; the cells of its inner surface were obviously instrumental in pro- 

 ducing the successive circumferential additions to the primary vascular 

 axis, whilst those of its outer surface increased the diameter of the 

 outer bark in the way just described. 



•After comparing these plants with living forms, the conclusion is 

 arrived at that the nearest parallel to the structure of their stems is to 

 be found in Psilotum triquetrum ; whilst their general affinities are 

 regarded by the author as Lycopodiaceous rather than Equisetaceous. 

 The exogenous aspect of their successive vascular growths is, if possible, 

 more conspicuous than in most of the other Carboniferous Cryptogams. 



The structure of the stems described is identical with that of those 

 found at Autun by Prof. Renault, and assigned by him to Sphenophyllum ; 

 thus the close affinity of this genus with AsteropJiyllites appears to be finally 

 established. The Catamites verticillatus of authors is probably the arbo- 

 rescent stem of one of these plants. 



