434 STRUCTURE OF STIGMAR1A. 



logical Survey most beautiful specimens of the vascular axis of Stiff- 

 marice, they were sliced for examination by Mr. Cuttle, and some of the 

 points they perfectly illustrate are drawn by Mr. Bone. 



Plate 2, fig. 4, represents the surface of the specimen in which the 

 axis Fig. 14 is contained. There was not the slightest appreciable dis- 

 tinguishing characters between the markings of this and that specimen 

 containing the very different looking axis Fig. 5. I shall therefore de- 

 scribe them as specifically the same, for in microscopical characters also 

 they are identical. 



The axis consists of a broad cylinder, composed of parallel elon- 

 gated tetragonal or hexagonal tubes, of equal diameter throughout, for 

 the o-reater part of their length obtuse and rounded at either extremity, 

 and everywhere marked with crowded parallel lines, which are free or 

 anastomising all over the surface. The tubes towards the axis are of 

 the smallest diameter: they gradually enlarge towards the circum- 

 ference, where the largest are situated, though bundles of smaller tubes 

 occasionally occur among the larger (Fig. 7 d). The cylindical axis 

 (which may for convenience be called the woody system of the plant) is 

 divided into elongated wedge-shaped masses, rounded at their posterior 

 or inner extremity by numerous medullary rays of various breadths, some 

 much narrower than the diameter of the tubes, others considerably 

 broader, but none are conspicuous to the naked eye, except towards the 

 outer circumference. 



The medullary rays, even the narrowest, are traversed by bundles of 

 tubes half the diameter of the largest vessels of the axis (or wood) or 

 even less (Plate 2, figs. 6, 7 a, and 8.) The transverse lines on their 

 surface are generally finer and less crowded. These bundles evidently 

 originate in the cellular axis of the stem, and do not belong to the 

 wedges of vascular tissue (or wood) between which they run, as they ap- 

 pear to have done in M. Brongniart's* specimen of the plant, both from 

 his figure and description. I cannot, however, but conclude the latter 

 to be erroneous, because M. Goeppert, whose specimens appear to have 

 been in this respect more perfect than any hitherto illustrated, repre- 

 sents the bundle of vessels which proceed from the axis, run between 

 the wedges of wood, and communicate with the rootlets (leaves, 

 Goepp.) as originating in isolated bundles, irregularly scattered in the 

 medullary axis of the stem. Of the existence of these bundles there 

 are some indications in my own specimens, though for the most part 

 they have been destroyed with the cellular tissue of the plant, wliich 

 indeed often takes place with the system of vessels from which the leaves, 

 rootlets, or scales of the cones in these fossils are supplied. It is so in 

 the stems of Lepidodendron, in the axis of the Lepidostrobi, in the 



* Archives du Museum d'Hist. Nat. v. i. p. 405, t. 29, f. 3 d. 



