PALEOZOIC COI^E-GENUS LEPIDOSTEOBUS. 219 



on the ventral side of the pedicel. Enclosed in a sheath of this tissue, it protrudes into 

 the parichnos space, which becomes reniform when seen in tangential section. 



Further from the axis, the pedicel widens to about 1'5 mm., the triangular form 

 becomes slightly modified, and the parichnos space disappears (PL 25. fig. 33 and PI. 86. 

 fig. 40). A very short dorsal keel is developed, and the dark sclerised tissue becomes 

 concentrated into two ventral cushions (sec.) lying to right and left of the attachment 

 of the sporophyll. Transfusion tracheides do not occur in the proximal region of the 

 pedicel, but they are abundant towards the distal end (PI. 25. fig. 35) and in the 

 upturned limb (PL 26. fig. 42). 



The sporophyll thickens considerably, where the lamina joins the pedicel, and the 

 upturned portion appears to have a thick median rib. In the sporophyll lamina the 

 tissue on the outer or dorsal side is dark and resistant, w^hile that on tbi ventral side, 

 which includes the bundle, consists of thin-walled cells. The arrangement of the cells 

 near both surfaces of the lamina suggests that periderm formation may have occurred 

 here to a slight extent (PL 25. fig. 36). 



(6) The Ligtile. 



A ligule is seen in one case in transverse section. It is enclosed in a ligular pit, and 

 its attachment is shown (PL 26. fig. 41). 



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(7) Tlie Sporangium. 



The sporangium is attached to the pedicel by a slender median ridge of tissue which 

 rises into the cavity of the sporangium {st.r., PL 25. fig. 33 and PL 26. fig. 40). This 

 ridge is bounded laterally by the wall of the sporangium, and may perhaps, as in 

 i. Binneyamis, be regarded as consisting of sterilised sporangial tissue (see p. 214). 

 Since dehiscence has taken place, it is difficult to examine the structures inside the 

 sporangium, but there is no doubt that an upgrowth of sterile tissue of plate-like form 

 arose from the floor of the sporangium [st.p., PL 25. fig. 33). 



The outer cells of the sporangial wall are of the usual columnar type, and sometimes 

 one or two layers of thin-walled cells are preserved internal to them. The columnar 

 layer is thicker where it approaches the supporting pedicel (PL 25. fig. 37 b) and thinner 

 on the ventral side (PL 25. fig. 37 a]. Dehiscence took place by means of a longitudinal 



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split along the median line of the upper surface (PL 25. fig. 32). 



(8) The Spores. 



Very few of the spores are retained, since the preparations are from cones that have 

 already dehisced. Some of the spores are shown in PL 25. fig. 39. They are slightly 

 bordered in the equatorial plane. Their maximum diameter is about 0028 mm. 



(9) Comparisoti with other Species of Lepidostrobus. 



The cone of Lepidostrobus gracilis is more slender in form than that of any other 

 member of the genus hitherto described as a petrifaction. The diameter is less than 

 1 cm., even in the case of a cone which was certainly mature, as most of the sporangia 



