v] BOTHRODENDRON AND ARCHAEOSIGILLARIA 65 



the unequal extension of the stem surface. . . .The [decorticated]^ 

 stem may show a marked fluting or ribbing which is connected 

 with the parichnos and bundle-strands, but ])ossibly also with 

 internal sclerotic bands. The calamitoid appearance of such 

 stems is increased by the presence of horizontal or trans- 

 verse ridges or zones which are, unlike the longitudinal ridges, 

 coincident with the surface leaf-scars and suggestive of nodal 

 diaphragms.... The [heterosporous]^ cone is terminal, and carried 

 on its broad (hollow?) axis numerous whorls of sporophylls, 

 of which the megasporophylls are the ones at present best 

 known." The sporophylls appear to be of a leafy type well 

 known in Lepidostrohus, bearing sporangia on the upper surface 

 of the basal portion. The distribution of mega- and microsporo- 

 phylls in the cone is at present unknown. 



With regard to the calamitoid appearance of certain decorti- 

 cated stems of this genus, we differ from Johnson who is inclined 

 to see in this feature some signs of affinity to the Sphenopsida. 

 These specimens appear to vis to represent sub-epidermal surfaces 

 which are not comparable with Calamite pith casts. Further in 

 many, but not all, Calamites, the external or sub-external 

 surface of the stem was not ribbed longitudinally 2. 



Neither the leaves, which are uninerved, long, linear structures 

 of the usual Lycopod type, nor the cones attributed to B. 

 Kiltorkense have as yet been found attached to the stems. The 

 former are believed to have been cadvicous. 



Distribution. Upper Devonian to Upper Carboniferous. 



Archaeosigillaria, Kidston, 1901 ^ (Figs. 38, 39, p. 66). Plants 

 with stems attaining a diameter exceeding 2-5 cm., dichotomously 

 branched. Stem covered with spirally arranged persistent leaf 

 bases; leaf bases contiguous, fusiform in younger branches, 

 hexagonal in older stems, bearing a single print situated slightly 

 above the centre of the leaf base. Leaves small, deltoid, markedly 



^ Inserted by the present author. 



^ At the same time there is no doubt that the occurrence of these ribbed 

 stems has eiven rise to the assertions of Heer and others that such genera 

 as Calamites or Archaeocalaniites occur in Devonian rocks, of wiiich, however, 

 there is no real evidence. 



3 For typical figures see Kidston (1885) and White (1907). 



A.D. F. 5 



