1 8 WATSON, Two Species of Lepidodendron Harcourtii. 



Lepidodendron, and Carruthers ('69) identified it with 

 L. selaginoides, Brong. 



The corona of L. Hickii is very similar to that of 

 L. vasculare, both being characterised by extreme blunt- 

 ness of the protoxylem points. The occasional occurrence 

 of isolated tracheids in the pith of L. Hickii is another 

 point of similarity with L. vasculare, Binney. 



The form of the leaf traces, starting as a cylindrical 

 mesarch bundle and then broadening tangentially into a 

 plate of tracheids, after passing through the phloem, is 

 the same in both species. 



It is thus seen that there are considerable resemblances 

 between the two species, which are, however, quite dis- 

 tinct, as shown by their outer cortices and the occurrence 

 of the dark secretory elements in the phloem of L. Hickii. 



The probable identification of L. Hickii with L. obo- 

 vatum renders the comparison of L. Hickii with the 

 specimen of L. obovatum described by Dr. Scott (Scott, 

 :06) of some interest. 



The two plants seem to differ in nearly all characters 

 which can be compared, notably in those of the protoxy- 

 lem points, which in L. obovatum of Dr. Scott are almost 

 as prominent as in L. Harcourtii. 



It is thus probable that the " species " L. obovatum 

 includes at least two widely different species. It should, 

 however, be pointed out that this does not affect any 

 value the Lepidodendrons may have as zonal fossils. 



From all other species the new species is separated by 

 the form of the corona and the character of the outer 

 cortex taken in conjunction. 



Resume. 

 Williamson's XIX. Memoir is examined, and it is 

 found that the specimens he described as shewing leaves 



