TRAQUAIRIA, SPOROCARPON. 177 



Keuper of N. Carolina may be such a sheath-bearing diaphragm of an 

 Equisetaceous plant. 



Casts of the broad medullary cavity of the stem are also extraordinarily 

 abundant, finely striated cylinders, which separate by sharp incisions into 

 portions answering to the internodes ; the striation, following the course of 

 the vascular bundles, is quite regular in its alternations. Each furrow in 

 such a cast may have come from a vascular bundle, which projected as a 

 slight rib on the wall bounding the medullary cavity. The incisions at the 

 nodes are the places where the homogeneity of the cast is interrupted by 

 the presence of the diaphragms. Objects in this state of preservation are 

 described in the older authors as Calamites arenaceus on account of their 

 resemblance to stems of Calamitae which we shall consider presently ; their 

 connection with Equisetites was first demonstrated by Petzholdt 1 and 

 Ettingshausen 2 . The latter states that he has seen Equisetitae in Bronn's 

 collection, which had a Calamites arenaceus inside it as an interior cast. 

 Portions also of the rhizomes of the plants occur frequently in a similar 

 state of preservation to that of the erect stems, and sometimes with the 

 lateral buds of the shoots attached 3 . They are distinguished, where the 

 surface can be seen, by the absence of the leaf-sheaths which were destroyed 

 at an earlier period, and by the numerous scars of larger branches and stems 

 present on the nodes. Together with all these remains there have been 

 found in the sandstones of the Keuper in many localities casts of the shape 

 of roundish usually somewhat flattened tubers often with folds on the 

 surface, which show an insertion-scar on one side and are of considerable 

 dimensions, though their size varies greatly 4 . Though these bodies have 

 never been found, as far as I know, actually attached to the rhizomes^ yet a 

 consideration of the facts in the case of Equisetites Burchardti, Dunk, is 

 sufficient to show that they are the well-known thickened portions of 

 rhizomes of our Equiseta. The Museum at Gottingen contains plates with 

 long pieces of the rhizome of this much smaller species, which is found 

 in the Wealden of Hanover, and to these are attached a number of the 

 roundish tubers which are similar in character to them. Schenk 5 gives a 

 figure of one of these rhizomes. Lastly, the soft gray clays of the Letten- 

 kohle of Basle have supplied, in company with numerous flattened stems of 

 Equisetites arenaceus preserved in their rind of coal, groups of the moulds 

 of polygonal scutiform bodies 6 , which are said to be the remains of the 

 fructifications of the stems. It is quite possible that this view is correct. 

 Each shield has a flat space in the centre (the apical surface), which is 

 bordered all round with narrow right-angled sloping planes answering to 

 the number of its sides. 



1 Petzholdt (1). 2 von Ettingshausen (.8). 3 Schimper (1), t. 10, f. 3. * Schimper 



(1), t. II, f. 4. 5 Schenk (1), t. 22, f. i. * Schimper (2), p. 162, f. \. 



N 



