128 The Root of Lyginodendron Oldhamium, Will. [May 31, 



the water value gives an expression for the sensitiveness of the instru- 

 ment. 



In Table VI the particulars of several air thermometers which I 

 have had made are given. As they are made of lead glass, both the 

 density and the capacity for heat are higher than in the case of 

 German glass. 



VII. " The Root of Lyginodendron Oldhamium, Will." By W. 

 C. WILLIAMSON, LL.D., F.R.S., and D. H. SCOTT, M.A., 

 Ph.D., F.L.S., F.G.S. Received March 14, 1894. 



During a re-investigation of the structure of Lyginodendron* 

 the results of which we hope to lay before the Royal Society on a 

 future occasion, an important fact has come to light, which we desire 

 to place on record without delay. 



A carboniferous fossil, with the structure perfectly preserved, has 

 been described in previous memoirs, under the name of Kaloxylon 

 HooJceri, Will.f We have now established the fact that Kaloxylon 

 was not an independent plant, but was the root of Lyginodendron 

 Oldhamium. 



Specimens, presenting in every respect the typical Kaloxylon struc- 

 ture, have been found in actual continuity with the stem of Lygino- 

 dendron^ arising from it as lateral appendages. Their structure and 

 mode of origin prove that they were adventitious roots. These 

 organs branched freely, and we have roots and rootlets of all sizes, 

 and at all stages of development. 



This discovery enables us to give a complete account of the vege- 

 tative organs of Lyginodendron, as we are now fully acquainted with 

 the structure, not only of the stem and foliage, but also of the adven- 

 titious roots. 



Presents, May 31, 1894. 

 Transactions. 



London : Camera Club. Journal. Vol. VIII. No. 96. 8vo. 



London 1894. The Club. 



Entomological Society. Transactions. 1894. Part 1. 8vo. 



London. The Society. 



Royal United Service Institution. Journal. Vol. XXXVIII. 



No. 195. 8vo. London 1894. The Institution. 



* Cf. Williamson, " On the Organisation of the Fossil Plants of the Coal 

 Measures," Part IV, ' Phil. Trans.,' 1873, p. 377; Part XVII, ' Phil. Trans.,' 1890, 

 B., p. 89. 



t Cf. " On the Organisation of the Fossil Plants of the Coal Measures," Part 

 VII, ' Phil. Trans.,' 1876, Part 1, p. 1 ; Part XIII, ' Phil. Trans.,' 1887, B., p. 289. 



