22 FOSSIL PLANTS. 



Specimen No. 1, is marked with the usual longitudinal ribs and furrows, interrupted by- 

 joints, so commonly met with on the exteriors of ordinary Calamites. This difference 

 in the outside appearance of large and small specimens is probably due to the extremities 

 of the pseudo-vascular bundles forming the ribs, and the lax tissue the furrows, in the 

 young specimens ; whilst the older individuals, having an exterior composed chiefly of 

 pseudo-vascular tissue without such marked divisions of cellular tissue, do not exhibit 

 such decided ribs and furrows. However diff'erent in appearance the outsides of the 

 specimens Nos. 1 and 3 are, we shall presently see that their structure is the same in 

 nearly all respects. 



Fig. 2 represents a transverse section of the stem, magnified ten diameters. It is oval 

 in form, and shows twenty-two wedge-shaped masses of pseudo-vascular structure, radiat- 

 ing from twenty-two different orifices, placed outside the central axis at regular distances, 

 and parted by wedge-shaped masses of lax tissue, increasing and diminishing in opposite 

 directions to what obtains in the pseudo-vascular tissue, as previously noticed in the 

 larger specimen No. 1 (p. 20). The tubes composing the latter tissue gradually 

 increase in size as they extend from the orifices towards the circumference ; whilst in 

 the lax tissue the cells diminish as they are traced from the outside of the central 

 axis to the exterior. 



The central axis has been destroyed, with the exception of two oval-shaped portions of 

 tissue, which, however, are too imperfectly preserved to afibrd us much evidence of their 

 original structure. Information as to this we shall receive from another and smaller 

 specimen hereinafter described. 



Fig. 3 represents a longitudinal section of the pseudo-vascular part of the stem 

 (magnified seven diameters), showing it to have been composed of quadrangular tubes, 

 having their sides marked by oval openings, placed horizontally, like those previously 

 described in No. 1 (p. 20). These tubes, when they approach the joints swell out; 

 but after they have passed those parts they assume their usual size. At the joints a 

 diaphragm of coarse cellular tissue appears to divide the stem horizontally, not much 

 unlike what is found in Badoxylon ; but, of course, less frequently, and at greater 

 distances. 



Fig. 4 show^s a tangential section of the stem, and affords evidence of the structure 

 of three of the bundles (oval in section) of vessels which proceeded from the joints to the 

 branches. These bundles, in their characters, both as to shape and structure, are like 

 those seen traversing the internal woody cylinder of Sigillaria vascularis, from the inside 

 to the leaves. This section also shows other masses, of a lighter colour than the body of 

 the specimen, and a more elongated oval shape, composed of three and four cells in 

 breadth. These appear to be extensions of the wedge-shaped masses of lax tissue which 

 divide the bundles of pseudo-vascular tissue near the orifices. One of these is shown 

 magnified forty-five diameters in fig. 6, and will afford a good idea of their general 

 appearance. 



