102 



LYCOPODIALES 



[CH. 



feature on Lepidodendron leaf-basest The diagram reproduced 

 in fig. 144, B, may be taken as practically correct, as the patches 

 of aerenchyma described by Weiss do not differ essentially from 

 the parichnos tissue. 



The parichnos scars are shown on the leaf-scar and cushion 

 in fig. 146, C. In the lower leaf-cushion shown in fig. 146, E, 

 the infra-foliar parichnos scars, p, are clearly seen, but the 

 preservation of the leaf-scar is not sufficiently good to show them 



It 

 P 



Qe ■ 



Fio. 145. A. Diagrammatic surface-yiew and longitudinal eection of a 

 Lepidodendron leaf-cushion. 

 B. Aerenchyma below the leaf-scar. (After F. E. Weiss.) 



on that part of the fossil. In the upper cushion (fig. 146, E) the 

 position of the parichnos arms is shown on the leaf-scar, but the 

 infra-foliar parichnos scars are hidden by two small spiral 

 shells. The genus Spirorbis, to which these shells are referred, 

 appears to have persisted from the Silurian epoch to the present 

 day. The comparatively frequent occurrence of Spirorbis shells 

 on the leaves and other parts of Palaeozoic plants, has recently 



1 For a fuller account of the parichnos, see Hill, T. G. (06) and other papers 

 quoted by F. E, Weiss (07). 



