HICK AND CASH : AFFINITIES OF LEPIDODENDROX. 
331 
Goebel" divides the Lycopodineee into three series, viz., Lycopo- 
diacew, Psilotacew and Ligukttce, and classifies Leindodendra as 
heterosporous Lycopodiacem. 
Van Tieghem,t on tlie other hand, divides the Lijdopodinpj.B into 
two orders, homosporous and heterosporous, and places Lepidodendmn 
in the latter, along with Isoetes and Selnginella. 
Thus while both agree to ignore the view that some Lepidodendra 
were homosporous, one attaches weight to the characters in which 
the}^ agree with Lycopodium, and the other to those in whicli they 
agree with Selctginella. That Lepidodendra sela(jnioide.-< does unite 
within itself anatomical and other features which Liicopi>diam and 
SrJ(u/i}?pUa divide between them is shown by the detailed comparison 
given above. The axile vascular cylinder and the correlated phyllotaxis 
approximate to those of Lycopodium, while the cortical tissues and 
the heterosporous fruits of some come nearer to those of Helagindla. 
It is difficult however to evaluate the rival claims of these similarities 
and differences. In our judgment the agreement of the vascular 
tissues is not of itself sufficient to warrant the association of Lepido- 
deridron with Lijcopodium as is done by Goebel ; nor on the other 
hand are the heterosporous fi'uits and the cortical resemblances 
sufficient to ally it with SelafiiupAla as is done by Van Tieghem. 
Probably the most that can be said, is, that the three genera have 
been derived through a series of intermediate forms from some 
common homosporous ancestor, from whom their common features 
have been inherited. But even on this hypothesis the facts at our 
command throw little light on the relationships of the diverging 
branches, and on their relative positions on the parent stock. We 
submit therefore, that until more precise knowledge bearing upon 
the affinities of these genera is obtained, and keeping in mind that 
homospory has not yet been positively disproved in Lepidodendmn, 
the grouping of the Lycopodinese should be somewhat as follows : — 
Lycopodinese. 
a. L)^copodiacea?. 
b. Psilotacese. 
* Outlines of Classification and Special Morphology, 
t Traite de Botanique. 
