144 



ANCIENT PLANTS 



Before leaving the palseozoic Lycopods another genus 

 must be mentioned, which is also a widely spread and 

 important one, though it is less well known than its con- 

 temporary. The genus Sigillaria is best known by its 

 impressions and casts of stems covered by leaf scars. 

 The stems were sometimes deeply ribbed, and the leaf 

 scars were arranged in rows and were more or less hexa- 



Fig. I02. — Cast and Reverse of Leaf Scars of Sigillaria. In A the shape of the 

 leaf bases is clearly shown, the central markings in each being the scar of the vascular 

 bundle and parichnos 



gonal in outline, as is seen in fig. 102, which shows a 

 cast and its reverse of the stem of a typical Sigillaria. 



In its primary wood Sigillaria differed from Lepido- 

 dend^^on in being more remote from the type with a 

 primary solid stele. Its woody structure was that of a 

 ring, in some cases irregularly broken up into crescent- 

 shaped bundles. The secondary wood was quite similar 

 to that of Lepidodendron. 



Stigmaria and its rootlet?^ belong equally to the two 

 plants, and hitherto it has been impossible to tell whether 



