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Prof. W. C. Williamson on the Fossil 



[June 19, 



leaves correspond exactly with what is seen in the ordinary specimens 

 found in the coal-shales. Transverse sections of them exhibit a single 

 thick central midrib, but no traces of vascular tissues have hitherto been 

 found in them. 



The laminae of the vascular axis are separated by numerous medullary 

 rays of small size ; these rarely exhibit more than four or five cells in 

 any vertical series, and usually but one or two. The exterior of the 

 bark is deeply indented in each internode by three very deep superficial 

 grooves, each one of which occupies the side of the stem corresponding 

 with a concavity of the central triangle of the vascular axis. These 

 grooves, which are sometimes double instead of single, extend from node 

 to node, but do not indent the nodal disks. Owing to the great depth 

 to which these penetrate the bark, they give a very characteristic tri- 

 partite aspect to each transverse section of these stems. 



The Burntisland type agrees with the Lancashire one in all its leading 

 features of structure and growth ; but its vessels are all barred instead 

 of being reticulated, and the author has not met with such beautiful 

 examples of its nodal disks as he has done in the case of the other form, 

 neither has he seen its leaves attached. On the other hand, he has 

 found specimens of much larger diameter than any that have hitherto 

 been detected in Lancashire, exhibiting the characteristic peculiarities 

 already referred to in an exquisitely beautiful manner. The author has 

 also obtained one section from this locality in which a branch is given 

 off. The vessels of this divergent organ are derived from the central 

 portion of one of the segments of small vessels, seen in the transverse 

 sections, which proceed from one of the angles of the central triangle. 



Having elucidated the details of the aerial stems, the author proceeds 

 to examine such organs of fructification as appear to belong to these 

 plants, commencing with the VoTkmannia Daivsoni, which he described at 

 length in the Transactions of the Philosophical Society of Manchester in 

 1871. This is a verticillate strobilus with a central vascular axis, of 

 which latter transverse sections exhibit a close correspondence with the 

 triangular bundle of Asterophyllites, being also triangular, with concave 

 sides and truncate angles. But in order to adapt this primary fibro- 

 vascular bundle to the requirements of the fruit, each of the truncate 

 angles is enlarged, so as to make the entire section an almost hexagonal one. 

 This axis is surrounded, as in Aster opliyllites, by a double bark — an outer 

 prosenchymatous one, and an inner one of more delicate cellular struc- 

 ture. At each node this bark expands into a lenticular disk fringed 

 with stiff narrow bracts, which extend upwards and outwards beyond 

 the sporangia. The latter rest upon the bractiferous disks and the basal 

 portions of the bracts, each verticil being fertile. The sporangia are 

 closely packed in about three concentric circles, and attached by sporangio- 

 phores originating from each side of the base of each bract. The 

 sporangia have cellular walls ; they are full of large spores, each of: 



