26 TRANSACTIONS. NATURAL HISTORY SOCIETY OF GLASGOW. 



future investigation. It is true that much is known about the 

 Carboniferous Lycopods, but many points still await careful 

 elucidation. 



We could all probably recognise a Sigillaria or Lepidodendron 

 in their typical forms were they placed before us, but how many 

 of us could clearly point out wherein these two genera differ 

 from each other? 



In my endeavours to work up the Carboniferous Flora of 

 Britain I meet with many collectors and students of fossil botany, 

 and have found that a great deal of confusion exists as to the 

 distinctive generic characters of some of the Carboniferous 

 Lycopods, and this has suggested to me that I might profitably 

 address you on this subject to-night. 



The genera which will be brought before you this evening are 

 of different values, for fossil plants usually occur in such a 

 fragmentary condition that it is frequently — most frequently, I 

 might say — impossible to refer the isolated leaves, fruits, and 

 rhizomes — the parts which help to make up a whole — to their 

 respective parent stems; hence it is necessary to place these 

 separated parts provisionally in special genera until their relation 

 to each other is ascertained. 



As we proceed these relationships will be pointed out as fully 

 as possible. 



EXISTING LYCOPODS. 



Before considering the structure and affinities of the Car- 

 boniferous Lycopods, it is necessary to consider briefly certain 

 points connected with the structure and growth of existing 

 Lycopods. 



These may be classified as follows : — 



LYCOPODIACEiE. 



A. Lycopodiece — with only one kind of spore ( Isosporous). 



Lycopodium. 



Tmesipteris. 



Phylloglossum. 



Psilotum. 

 B Selaginellece — with two kinds of spores (Heterosporous). 



Selaginella. 



Isoetes, 



