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Proceedings of the Royal Society of Edinburgh. [Sess. 
base is followed in this section it will be found to be continuous below with 
the margins of the sporophylls to right and left. Since, however, the tissue 
of the sporophyll-base and of these margins has been entirely replaced by 
mucilage, the outline is only to be traced in the mature cone by the 
structureless membranes bounding the mucilaginous mass. The sporangium 
bulges upwards into the mucilaginous sporophyll-base situated vertically 
above. The only persistent portion of the sporophyll-base shown in 
tangential section is the pedicel-like part enclosing the vascular bundle. 
At the plane of this section (fig. 2), which is that of the insertion of the 
sporangia, the cross-section of this persistent “ pedicel ” is more flattened 
than it is between the sporangial attachment and the axis ; in that region 
it is usually irregularly rectangular in outline. Study of sections of cones of 
different ages leaves no doubt that the sporophyll-bases are coherent, so that 
each sporangium lies in a pocket open only on the outer surface of the cone. 
This pocket is bounded below by the upper surface of the sporophyll-base 
to which the sporangium belongs; above by the lower surface of the 
sporophyll-base immediately above on the same orthostichy (i.e. the 
sporopliyll belonging to the whorl next but one); and laterally by the 
dependent sporophyll-bases with their mucilage sacs of the alternating 
sporophylls belonging to the next higher whorl. 
In the light of the radial and tangential sections, the two transverse 
sections, which are made at the two levels indicated on the radial section, 
will be intelligible and convey further information. In fig. 3 the section 
(made in the plane A A in fig. 1) has passed through the sporangia of 
one whorl ( b ), the lamina belonging to each sporangium being seen on 
the same radius. Between the sporangia are the five dependent bases of the 
alternating whorl of sporophylls above (a). The section has passed through 
