52 SCIENCE PROGRESS. 



nature of Halonia, but unfortunately the author had not 

 seen the last contribution on the same subject by Prof. 

 Williamson. 



After speaking of the various suggestions as to the 

 nature of Halonial axes, Potonie expresses his belief that 

 such structures only occur in connection with Lepidophlows, 

 and not with Lepidodendron stems : he suggests the ad- 

 visability of re-examining the specimen in the Leeds 

 Museum which Williamson figured in 1883, 1 as proving 

 the organic continuity of Halonia and Lepidodendron. 

 Another addition to previously incomplete knowledge is 

 made by Williamson with regard to a curious form of 

 Lepidostrobus*- belonging" to that type of vegetative axis 

 named by him in 1889, 3 Lepidodendron Spenceri. It is 

 shown that we have in this plant not only a well-defined 

 form of stem structure, but also an equally well-marked 

 type of strobilus characterised by its winged spores and 

 other peculiarities of structures. 



We are indebted to Prof. Bower 4 for an exceedingly 

 interesting account of a species of Lepidostrobus, — L. 

 Brownii Schmp. preserved in the British Museum, and 

 known as " Brown's Cone " ; he gives a detailed descrip- 

 tion of the axial structures, and dwells at length on certain 

 features characterising the well-defined cortical tissues. 

 The general structure of the stele of L. Brozvnii seems 

 to agree fairly closely with Lepidodendron Williamsoni? 

 Occupying the centre of the strobilus axis is a parenchy- 

 matous pith with a ring of primary xylem giving off leaf- 

 traces from its outer crenulated margin. Surrounding 

 this cylinder of tracheids Bower describes a somewhat 

 meagre development of phloem, and draws attention to 

 certain cells enclosing the whole stele which exhibit 



1 Phil. Trans., 1883, pt. ii., pi. xxxiv. 



2 Ibid.) 1893, B, p. 24. 



3 Ibid., vol. clxxx., 1889, B, p. 199. 



4 Annals Bot., vol. vii., 1893, p. 329. 



5 Solms-Laubach, Fossil Botany, p. 226. 



