498 SECTIONAL TRANSACTIONS.— K. 



Petioles of Lyginorachis type are inserted in the stem almost opposite one 

 another ; and each pair is set at right angles to the preceding and the suc- 

 ceeding pairs. A pulvinus occurs at the base of the petiole ; and the petiole 

 bifurcates at a distance of some 5^ in. from its insertion into the stem. 

 Primary pinnae are developed, in an alternating series, in each branch of the 

 petiole. No laminar structure has been found so far. 



No fructifications have yet been discovered in actual continuity with the 

 petioles, though synangia that may possibly belong to the plant occur in 

 association. 



Correlation is suggested with Telangium affine, L. & H. sp., mainly on 

 the ground of the characters of the cortex, but such correlation is not 

 stressed meanwhile. 



An interesting mineralogical feature is the presence of analcime as a 

 petrifying medium. Analcime has been recorded as a sedimentary deposit 

 in what were ancient saline lakes, but never before as the petrifying material 

 of fossil plants. Another point of mineralogical import is that the un- 

 weathered character of the adventitious felspar grains in the ashes, as com- 

 pared with the weathered condition of the felspars of the ash fragments, 

 appears to indicate that the climate in the neighbourhood of the volcanoes 

 was semi-arid and this is confirmed by the plant types in the ashes. 



The geological horizon is low down in the Calciferous Sandstone Series, 

 perhaps in the Cementstone Group, but certainly low in the Oil Shale 

 Group. 



A full account will be found in the Transactions of the Royal Society of 

 Edinburgh. 



Mr. N. W. Radforth. — An analysis and comparison of the structural 

 features of Dactylotheca plumosa Artis and Senftenbergia ophiodermatica 

 Gopp sp. (12.15). 



Of these two carboniferous fern-like compressions, the former has been 

 regarded as a true fern with annulate sporangia, while the latter was believed 

 to be a Pteridosperm from the nature of its apparently exannulate sporangia. 

 However, this analysis has shown that the fructifications of Dactylotheca 

 plumosa are definitely annulate and identical with those of Senftenbergia. 

 Moreover, it is clear that these two fossils are merely different parts of the 

 same plant, and can no longer be regarded as belonging to separate genera. 

 Since the name Senftenbergia has priority, this genus must now embrace 

 the forms previously described as Dactylotheca plumosa. The spores, 

 which hitherto had not been revealed, have been isolated from the sporangia 

 in their various developmental stages. Both the sporangia and the mature 

 spores resemble so closely those of the living fern Aneimia that the view of 

 a possible relationship between Senftenbergia and the living schizaeaceous 

 ferns to which Aneimia belongs, is now greatly strengthened. 



Afternoon, 



Dr. Ralph Emerson. — Life cycles in the Blastocladiales (2.15). 



The phycomycetous order Blastocladiales embraces three genera of 

 aquatic fungi, Allomyces, Blastocladia, and Blastiocladiella. The types of 

 sexual reproduction and the life cycles which have been discovered in 

 certain members of this group are unique in the filamentous Phycomycetes. 



