18H5.] Lyginodendron and Heterangium. 195 



and near the poles were changed. From the capillary there was but 

 a feeble glimmer, not of an orange tint, while the orange tint was 

 now observed near the poles, the poles themselves being obscured 

 by a coating on the glass of brilliant metallic lustre. 



After attempting in vain for some time to determine the cause of 

 the inversion of D 3 and 447 in various photographs I had obtained 

 of the spectra of the products of distillation of many minerals, it 

 struck me that these results might be associated with the phenomena 

 exhibited by the tube, and that one explanation would be rendered 

 more probable if it could be shown that the change in the illumina- 

 tion of the tube was due to the formation of platinum compounds, 

 platinum poles being used. On May 21st I accordingly passed the 

 current and heated one of the poles, rapidly changing its direction 

 to assure the action of the negative pole, when the capillary shortly 

 gave a very strong spectrum of hydrogen, both lines and structure. 

 A gentle heat was continued for some time and apparently the 

 pressure in the tube varied very considerably, for as it cooled the 

 hydrogen disappeared and the D 3 line shone out with its pristine 

 brilliancy. The experiment was repeated on Ma.y 24th and similar 

 phenomena were observed. 



III. " Further Observations on the Organisation of the Fossil 

 Plants of the Coal-measures. Part III. Lyginodendron 

 and Heterangium" By W. C. WILLIAMSON, LL.D., F.R.S., 

 Emeritus Professor of Botany in the Owens College, Man- 

 chester, and D. H. SCOTT, M.A., Ph.D., F.R.S., Honorary 

 Keeper of the Jodrell Laboratory, Royal Gardens, Kew. 

 Received May 14, 1895. 



(Abstract.) 



Introduction. 



The two genera, Lyginodendron and Heterangium, are among the 

 most interesting and at the same time the most puzzling representa- 

 tives of the Carboniferous flora. Although we are still without any 

 satisfactory evidence as to the reproductive organs in either genus, 

 yet the organisation of their vegetative members is preserved with 

 such completeness and perfection as to show that these fossils 

 present a combination of characters such as exists in no living group 

 of plants. 



The evidence afforded by the vegetative characters clearly points 

 to a position intermediate between ferns and Cycadeee. 



