274 STIGMARIA. 



very seldom preserved. Figures giving the details of such cases will be 

 found in Williamson \ The inner layer, composed probably of loose paren- 

 chyma, is always entirely destroyed and its place occupied by structureless 

 stone. This is usually the case also with the ring of bast, though I have 

 seen tolerably distinct remains of this portion of the rind in a specimen 

 belonging to the collection at Strassburg. The outer rind on the other 

 hand which bears the appendages is, when present, generally well-preserved. 

 It consists of an outer layer of isodiametric thick-walled parenchyma, and 

 an inner tissue composed of radially disposed parenchyma-cells. The 

 former may answer to the primary rind, the latter will be the product of 

 a secondary zone of meristem on its inner margin. The boundary-line 

 between them is very distinctly marked in longitudinal sections 2 because 

 of the difference of form in their elements, which in the primary parenchyma 

 are isodiametric, in the inner layer on the contrary are elongated. The 

 entire rind is of course traversed by the traces which pass out into the 

 appendages, and which here too, so far as we know from our present re- 

 searches, show secondary growth, and consequently maintain unchanged the 

 characteristic form of the isosceles triangle with the acute angle pointing 

 inwards. Of the course of the traces in the inner rind which has dis- 

 appeared we learn something from single specimens in a peculiar form of 

 preservation. There is a magnificent specimen of this kind to be seen in 

 the Museum at Breslau. This is an interior cast found in 1884 at the mine 

 named Wildsteiner Segen in Upper Silesia ; it is formed of fine-grained 

 slate-clay, and is split exactly in the radiate direction. The outer cast 

 contains a number of very delicate linear traces preserved in coal, which 

 pass through it in shallow curves with an outward direction, and are 

 partly it is taie displaced and irregularly confused together. These are the 

 traces running to the appendages, which resisted decay longer than the 

 surrounding tissue, and were inclosed in the matter forming the cast. 

 Similar specimens are given in Goppert 3 , and Williamson 4 figures one of 

 the kind, but it is not so well preserved. On the same table Williamson has. 

 given two more figures exemplifying another closely allied state of preser- 

 vation. One of these is a petrified piece of wood, the other a piece of the 

 outer rind seen from the inside. Both are covered with irregularly curved 

 flattened vermiform cylindrical bodies, the petrified remains of the traces 

 traversing the inner rind, which has otherwise disappeared ; the traces are 

 also incrusted by surface-addition of the petrifying material. Exactly the 

 same state preserved in clay-ironstone is described in Lindley and Hutton 5 

 as Caulopteris gracilis. 



1 Williamson (6), tt. 6, 8, and (1), II. t. 31, f. 52. Williamson (6), t. 6. s Goppert (1), 

 t. 10, f. 17, and t. n, f. 18. * Williamson (6), t. ia. 8 Lindley and Hvjtton (1), vol. ii, 



t. 141. 



