SIGILLARIA. 



101 



similar to what Corda had described in his specimen, had occupied them, none were 

 seen. The rays, whether the large oval or the small ones, consisting of a series of single 

 or double cells in a vertical line, were not distinctly shown in the longitudinal section, 

 however large, but only in the tangential sections, which is rather singular. The 

 larger or primary rays in the inner radiating cylinder were in no case absolutely traced 

 to those traversing the outer cylinder, but in the small S. vascularis, figured in the 

 woodcut No. 5 (p. 594), they were distinctly seen proceeding from the outside of the 

 inner to the exterior of the outer radiating cylinder. Still, they were not absolutely 

 proved to be connected with the inner primary rays. These latter, as previously stated, 

 were only seen in tangential section, so it is difficult to speak with certainty whether they 

 were composed of barred tubes or not. 



Since the publication of my Memoir all my specimens of Diplox^Iou and Sigillaria 

 have been again carefully examined in their longitudinal sections, and traces of vascular 

 bundles like those so frequently found in common Siif/inaria, and which form so 

 marked a character in Corda's DiploxyJon cycado'ideum , have been found ; but certainly 

 not so distinctly, or communicating with the medulla, as shown in the transverse and 

 longitudinal sections of his specimens. 



In the outer radiating cylinder, or inner bark, the foliar bundles, enveloped in masses 

 of very large and lax parenchyma, of a double-cone form, noticed by Professor King, are 

 seen traversing the prosenchymatous tubes and pushing them aside; but these are 

 shown chiefly in the tangential section, although a few traces of them are met with in the 

 longitudinal section. One of the best examples hitherto met with is that figured in 

 plate 34, fig. 2, of my Memoir in the 'Phil. Trans.' for 1865. These characters 

 are much the same, whether observed in the large specimens, with irregular ribs and 

 furrows, or those with rhomboidal scars on their outsides, like fig. 5, in plate 35, 

 of that Memoir ; thus showing, by their structure, that both specimens most probably 

 belong to one plant. In the midst of this lax tissue the bundle of vascular tubes, in 

 •tangential section, presents a kidney shape, similar to what MM. Renault and 

 Grand' Eury have noticed in Sigillaria sjnnulosa. In none of ray sections, however, has 

 there been seen any indication of the anastomozing observed by those authors in trans- 

 verse and longitudinal sections of their specimen. 



As the stems grow larger the lax cellular tissue enveloping the foliar bundles becomes 

 less, so that in an outer radiating cylinder, five to six inches in breadth, little of it is 

 seen ; and what does appear is far more compact in structure than the very large cells 

 of lax parenchyma seen nearer the centre. The wedge-shaped masses of parenchyma 

 containing the foliar bundles of vascular tissue divide the wedge-shaped masses of 

 prosenchymatous tissue ; and these wedges have their thin and thick ends opposite to 

 -each other, the one increasing inwards and the other outwards. It is most probable, 

 owing to the very large size of the cells of this lax parenchyma, that the space between, 

 the inner and outer radiating cylinders in S. vascularis is so often wanting in structure. 



