90 LYCOPODIALES [CH. 



sporophyll region of the axis reached a length of at least 12 cm. 

 The spirally disposed sporophylls terminate in a rhombic distal 

 end which may represent the original termination or they 

 may have been prolonged upwards as free laminae. Each 

 sporophyll bears on its upper face a single large sporangium 

 containing either megaspores or microspores: the megaspores, 

 0*55 — 0'60 mm. in diameter, are finely granulate and bear small 

 warty thorns or more slender pointed appendages. The micro- 

 spores, after treatment with eau de Javelle, were found to 

 measure 36 — 44/* while others which had been treated with 

 ammonia reached 54/^ in diameter. Nathorst describes the 

 microspores as occurring in spherical groups or balls, which 

 it is suggested may be compared with the groups of spores 

 separated by strands of sterile tissue (trabeculae) in the large 

 sporangia of Isoetes (cf fig. 133, H). If this comparison is sound 

 it would point to a more complete septation of the sporangium 

 in Lycostrohus than in any recent species of Isoetes. The size 

 of the strobilus would seem to indicate the persistence into 

 the Rhaetic era of an arborescent lycopodiaceous type ; but the 

 appearance and manner of preservation of the axis is inter- 

 preted by Nathorst as evidence of a herbaceous rather than 

 a woody structure. He is disposed to regard Isoetes as the 

 most nearly allied existing genus. 



The comparison made by Nathorst with Isoetes is based on 

 a resemblance between the spores of the two genera and on the 

 evidence, which is not decisive, of the existence of sterile 

 strands of tissue in the sporangia of Lycostrohus. This 

 similarity is however hardly of sufficient importance to justify 

 the inclusion of the Rhaetic strobilus in the Isoetaceae. In 

 size and in the arrangement and form of the sporophylls the 

 cone presents a much closer resemblance to Lepidodendron than 

 to Isoetes. It is probably advisable to regard this Rhaetic 

 type simply as a lycopodiaceous genus which we are unable, 

 without additional information, to assign to a particular position. 



The opinion expressed by Professor Fliche' that the plant 

 described by Schimper and Mougeot as Gaulopteris tessellata, 

 a supposed tree-fern stem, from Triassic rocks of Lorraine, is 



1 Fliche (03). 



