776 itEPOKT— 1892. 



3. On the Structure of the Stem of a Typical Sigillaria. 

 By W. Carruthees, F.B.S. 



4. Calamostachjs Binneyaua {Schimp.). By Thomas Hick, B.A., B.Sc. 



The object of this paper is to revife our knowledge of the structure and affi- 

 nities of Calamostachys Binneyana in the light of a series of preparations which 

 have not hitherto been described or published. 



The spike consisting of an axis surrounded by alternating whorls of bracts and 

 sporangiophores, the structure of each of these is examined in detail and compared 

 with the descriptions already published by Carruthers, Biuney, and Williamson. 



The central part of the axis, hitherto described as vascular, the author tinds to 

 be cellular, and to form a true pith which is circular or triangular in the transverse 

 section. 



Round the pith are, usually, three primary Avascular bundles, which are reduced 

 to the condition of those met with in ihe stems of Equisefjim and the youngest 

 branches of Catamites, i.e., to as many carinal canals, with annular or spiral 

 vessels adhering to the wall. AVhen secondary thickening occurs it commences 

 at these carinal canals, and usually three wedge-shaped masses of secondary 

 xylem are first formed; subsequently these may be united to form a- complete 

 zone. 



The cortical tissues of the axis, the 'nodal discs,' the bracts, and the sporangio- 

 phores are described with additional detail, and special attention is called to a 

 layer of large cells, often with black contents, which is found uear the margin of 

 the ' nodal discs,' and forms the lower or outer half of the bracts. 



A few additional details are also given of the structure of the sporangia, the 

 most important of which is the presence of a small mass of non-sporogenous tissue 

 at the proximal end, where the sporangia are contracted into the peduncles. 



As to the afHnities of the spike, the structure described is held to demonstrate 

 that it belongs to some carbonilerous plant whose affinities are more or less close 

 with the existing genus Equisetum. Such a plant we have in Calamites, to which 

 the spike was referred by Carruthers in 1867. Against this determination AVil- 

 liamson set the vascular structure, as it was then interpreted, of the central part 

 of the axis, and, relying on this, referred Calamontachys Binneyana to the Lyco- 

 podiaceaj. The proof now adduced that the centre of the axis is cellular removes 

 the objection raised by AVilliamson and brings us back to Calamites. The discovery 

 of carinal canals at the periphery of the pith, as representatives of the primary 

 vascular bundles, gives all that is needed to conlirra this view, and leaves little or 

 no doubt tliat Calamostachys Binneyana is the fruit of some form of Calamites. 



Beyond this it is difficult to go. There are, however, two facts thfit suggest 

 that the spilie is ]>robably tlie fruit of a Calamites of the Arthropitys type. These 

 are (i.) that Arthropitys is the only form with structure found in Yorkshire and 

 Lancashire where Calamostachys Binneyana is met with; and (ii.) that in the stems 

 and leaves of Arthropitys we have a layer of large cells, with frequent black 

 contents, such as are found in the nodal discs and bracts of the spike. 



5. Notes on Specimens of Myeloxylon (Brong.) from the Ilillstone Grit and 

 Coal-measures. By A. C. Seward, M.A., F.O.S. 



A number of specimens of IMyeloxylon examined by the author lend support 

 to the views of Schenk and others, that the anatomical structure of this fossil 

 plant agrees more closely with that of cycadean petioles leather than with the' 

 petioles of ferns. Whilst recognising a number of characters which suggest a 

 cycadean affinity, there are noted one or two points which render it probable that 

 Myeloxylon may eventually find its true position intermediate between ferns and 



