158 Mr Seward, Notes on the Binney Collection 



Part II. Megaloxylon, gen. nov. 

 Plates V — VII and Text-figures 1 — 4. 



I. Descriptive. 



The following description is based on the examination of ten 

 sections prepared from a fragment of stem in the Binney Collection. 

 In looking through the numerous unlabelled slides I found one 

 thick transverse section which at first sight was taken for that of a 

 Gordaites stem with a thick zone of secondary wood enclosing a large 

 pith ; but a closer inspection of the slide at once revealed certain 

 peculiarities which suggested a comparison of the specimen with 

 the genus Heterangium. The block from which the single section 

 had been obtained was fortunately found in the collection, and two 

 additional transverse sections and seven longitudinal sections were 

 cut from it by Mr Lomax of Bolton 1 . The stem fragment occurs 

 in a calcareous matrix associated with the shells of Goniatites, and 

 was originally obtained from the Lower Coal-Measures of Lan- 

 cashire. Unfortunately the specimen does not afford any indication 

 of the nature of the cortical tissues, which had become separated 

 from the secondary wood before the fragment was embedded in cal- 

 careous mud. The central region of the stem, which at first suggested 

 a resemblance to a large Gordaites pith, consists of primary 

 xylem ; this is surrounded by a cylinder of secondary wood 

 ending abruptly at the margin of the specimen. The complete 

 section measures 4'8 cm. by 4*2 cm. ; the greatest diameter of the 

 central region (primary xylem) being 1'9 cm., the secondary xylem 

 having a breadth of 2 cm. 



Fig. 2, PI. v. shows the appearance of the specimen in trans- 

 verse section. The central region x l is occupied by tracheids and 

 parenchyma, and surrounding this primary xylem there is a broad 

 cylinder of secondary wood, part of which is imperfectly pre- 

 served ; the reticulum of dark lines in the secondary wood — seen 

 on the left in the photograph — is caused by secondary crystallisa- 

 tion in the mineral matrix, which has partially destroyed the 

 xylem tissues' 2 . The denser oval group of elements at the peri- 

 phery (fig. 2, It) of the primary stele represents a leaf-trace about 

 to pass outwards through the secondary xylem. In fig. 1, PL v. 

 part of the stem is shown (natural size) in longitudinal section ; 



1 The sections are referred to in these notes as 1. 1, I. 2, I. 3 (transverse 

 sections) and I. 5 — 1. 10 (longitudinal sections). 



2 Cf. Seward (98), p. 81. 



