204 LYCOPODIALES [CH. 



strands (fig. 198) which are sometimes partially or wholly- 

 fused into one (Syringodendron state of Sigillaria). The single 

 or double nature of the elliptical or circular parichnos areas is 

 doubtless due to the degree of exfoliation, which may extend 

 sufficiently deep into the cortex to reach the level of the 

 parichnos before the single strand has bifurcated (of Lepido- 

 dendrvn, p. 100). In the Museums of Manchester, Newcastle, 

 and other places casts of large Sigillaria stems may be seen, 

 which illustrate the differences in breadth and regularity of the 

 vertical ribs, and in the size and shape of the parichnos areas 

 in different regions of a partially decorticated stem. A cast of a 

 ribbed species in the Manchester Museum, having a length of 

 185 cm. and a breadth of 56 cm., shows in the upper portion 

 straight vertical gi-ooves and broad ribs bearing pairs of parichnos 

 scars 11 mm. long; in the lower portion the ribs tend to 

 become obliterated and the parichnos scars, 2 cm. in length, 

 may be partially fused and arranged in much less regular vertical 

 series. A feature of these older ribbed Sigillarian stems is the 

 increase in the number of the ribs from below upwards. Kidston ' 

 has described a specimen in the Sunderland Museum, 6 feet 

 6 inches long, with a circumference at the slightly bottle-shaped 

 base of 5 feet. On the lower portion of the stem there are 

 29 broad ribs; about one-third the height many of these 

 bifurcate, producing as many as 40 ribs in the unper part 

 where the cast has a circumference of 3 feet. The increase 

 in number of the ribs is due in part to bifurcation, but also 

 to the intercalation of new ones. As Kidston points out, this 

 example shows that as a stem grew in length additional leaves 

 were developed at the apex. A similar stem, which illustrates 

 very clearly the increase in the number of ribs from below 

 upwards, may be seen in the Newcastle Museum. 



Grand'Eury^ has described an example of an old stem of a 

 ribless species of Sigillaria, Syringodendron bioculatum, bearing 

 single and double parichnos areas of nearly circular form and 

 with a diameter of 1 — 2 cm. In a specimen figured by Renault 

 and Roche' {Syringodendron esnostense) from the Culm strata 



1 Kidston (97) p. 46. « Grand'Eury (90) A. PI. xni. fig. 8. 



' Benault and Boche (97). 



