1891.] of the Fossil .Plants of the Coal-measures. 155 



not only no midrib, but they seem to contain no traces whatever of a 

 vascular bundle. 



The centre of the axis of the strobilus is occupied by a conspicuous 

 bundle of barred and reticulated tracheids of the scalariform type, the 

 transverse section of which bundle is triangular, with concave sides. 

 Each of the three prominent angles is abruptly and broadly truncated. 

 A thin inner cortex seems to have originally surrounded this bundle, 

 but all traces of its tissues have disappeared. The thick outer cortex 

 is composed of a mixture of rather coarse, strongly defined parenchy- 

 matous and prosenchymatous cells. At each node this cortex expands 

 into the lenticular disk already referred to. This disk is thickest at 

 its inner border, thinning gradually towards its outer margin, where 

 it subdivides into the verticil of elongated disk-rays already men- 

 tioned. Though no vascular bundles can be discovered connecting 

 the central axial one with the surrounding disk, some such must 

 have once existed, since we find them both in the cortex of the inter- 

 nodes and in the nodal disks. 



The entire upper surface of each disk has given off numerous very 

 slender sporangiophores, destined to reach three or four concentric 

 circles of sporangia, which were arranged in a single plane in the 

 internodal interval between each two disks. Each sporangiophore, 

 unlike what is usual amongst the Calamariae, only sustained a single 

 sporangium. In order to reach the more external ranges of the latter 

 organs, the sporangiophores were prolonged outwards in a distinct 

 layer between the upper surface of the disk and the sporangia which 

 rested upon it. N"ot only was this the case, but when each sporangio- 

 phore reached the sporangium with which it was destined to become 

 organically united, it did not at once do so ; but it passed under, and 

 even beyond that organ, when it bent back upon itself and became 

 united to the sporangium on its distal side. The outer, or epidermal, 

 layer of the sporangium was merely an extension of that of the 

 -sporangiophore. 



The numerous spores of Bowmanites have also a distinctive form. 

 Each has a rather thin exosporium, but this is thickened along a few 

 reticulate lines, and from each junction of these reticulations a strong 

 radiating spine is projected. Jt is in the very distinctive features of 

 these reproductive organs that the marked generic individuality of 

 Bowmanites chiefly resides. 



The second plant described in the memoir, under the name of 

 Jtachiopteris ramosa, is one of the several Fern-like organisms which 

 the author has included in his provisional group of fi-achiopterides. 

 Considerable doubt exists respecting the true affinities of at least 

 some of these plants. The one now described may prove to be a less 

 hirsute, more fully developed condition of the Rachiopteris hirsuta 

 described by the author in his Memoir XV. 



