STRUCTURE OE LEPIDOSTEOBUS. 360 



organs which are commonly crushed or destroyed even in those specimens showing good 

 axial structures. 



So far as the origin of the bundles and their passage through the inner space, inner 

 cortex, middle cortical space, and outer cortex is concerned, there is nothing to distinguish 

 this from the (a) form before described. The bundles traversing the middle cortical space 

 distinctly show the remains of two sheaths : one surrounding the xylem only, and the 

 other, the ordinary inner cortical sheath, investing the whole bundle. 



PI. XXXVIII. fig. 29 is a vertical section of a bundle in this region ; it does not pass 

 centrally through the bundle, and so escapes the phloem space ; it shows, however, the 

 mesarch nature of the xyJem, £c., and the cells of the inner cortical sheath, i.c.sh. 



Examination of the radial section preserved in the Binney Collection at Cambridge 

 shows indications of the same peculiar arrangement of cells between the xylem and phloem 

 of the leaf-trace when in the outer cortex, as is ilhistrated on PI. XXXVII. fig. 14 in 

 Lepidostrobtis oldhamius (a). 



PI. XXXVllI. fig. 30 is part of a tangential section of the cone, magnified ten times. It 

 shows the pedicels, cut approximately in transverse section, each supporting a single 

 sporangium on its upper surface. Each sporangium is filled with spores. 



PI. XXXVIII. fig. 31 is an enlarged drawing of one of the sporophylls and adjacent 

 sporangia, from the same section as that figured by Williamson, '* Organization," &c., 

 Part XIX. pi. 6. fig. 61. The pedicel is cut transversely, and the section passes so near the 

 main axis of the cone as to escape the attachment to the sporangium. It exhibits a 

 triangular form, and consists mainly of a sclerotic cortex, <?., continuous with the outer 

 cortex of the axis. The vascular bundle is seen towards the upper surface, the xylem, x. 

 being preserved, while the phloem, p., is represented only by a space. Surrounding the 

 whole bundle is a parenchymatous sheath, ^.c.s^., doubtless representing the inner cortical 

 sheath. Below this is seen the large parichnos space. Pa., which was doubtless originally 

 filled with tissue continuous with the middle cortex of the axis. 



The parichnos in the vegetative region of Lepidodendron has been described by 

 Bertrand *, Hovelacque f , and Williamson $, who have shown that the leaf-trace while 

 traversing the outer cortex of the stem is accompanied by a distinct strand of specialized 

 cells, and that before entering the leaf-base this strand, whicli Bertrand named the 

 parichnos, bifurcates, the two arms bending away right and left of the leaf-trace, so that 

 the bundle in the cushion (leaf base) is accompanied by two strands of tissue, one on either 

 side. There is no indication of such a bifurcation in the parichnos of the sporophyll ; this 

 difference may, perhaps, be correlated with the small width of the proximal end of the 

 pedicel as compared with that of the leaf-base on the vegetative stem. 



PI. XXXVIII. fig. 32 is a section similar to the last, but cut at a somewhat greater 

 distance from the axis. (N.B. This drawing is magnified to more than double the scale of 

 fig. 31.) The pedicel has here lost its triangular outline and is becoming distinctly winged, 

 while above, the attachment is shown to the sporangium. Apart from these differences, 



* Trav. et Mem. Facult. Lille, vol. ii. (1891), Mem. 6. 



t M«3m. Soc. Linn. Normandie, 1892. 



t " Organization," &c., Part XIX., Phil Trans. 1393. 



